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Allow hints to be placed anywhere in query
[pghintplan/pg_hint_plan.git] / pg_hint_plan.c
index 0c5f886..0852f56 100644 (file)
@@ -3,7 +3,7 @@
  * pg_hint_plan.c
  *               hinting on how to execute a query for PostgreSQL
  *
- * Copyright (c) 2012-2018, NIPPON TELEGRAPH AND TELEPHONE CORPORATION
+ * Copyright (c) 2012-2021, NIPPON TELEGRAPH AND TELEPHONE CORPORATION
  *
  *-------------------------------------------------------------------------
  */
@@ -12,6 +12,7 @@
 #include "postgres.h"
 #include "access/genam.h"
 #include "access/heapam.h"
+#include "access/relation.h"
 #include "catalog/pg_collation.h"
 #include "catalog/pg_index.h"
 #include "commands/prepare.h"
 #include "miscadmin.h"
 #include "nodes/nodeFuncs.h"
 #include "nodes/params.h"
-#include "nodes/relation.h"
 #include "optimizer/appendinfo.h"
 #include "optimizer/clauses.h"
 #include "optimizer/cost.h"
 #include "optimizer/geqo.h"
 #include "optimizer/joininfo.h"
+#include "optimizer/optimizer.h"
 #include "optimizer/pathnode.h"
 #include "optimizer/paths.h"
 #include "optimizer/plancat.h"
@@ -37,6 +38,7 @@
 #include "partitioning/partbounds.h"
 #include "tcop/utility.h"
 #include "utils/builtins.h"
+#include "utils/float.h"
 #include "utils/lsyscache.h"
 #include "utils/memutils.h"
 #include "utils/rel.h"
@@ -92,6 +94,8 @@ PG_MODULE_MAGIC;
 #define HINT_LEADING                   "Leading"
 #define HINT_SET                               "Set"
 #define HINT_ROWS                              "Rows"
+#define HINT_MEMOIZE                   "Memoize"
+#define HINT_NOMEMOIZE                 "NoMemoize"
 
 #define HINT_ARRAY_DEFAULT_INITSIZE 8
 
@@ -120,7 +124,8 @@ enum
 {
        ENABLE_NESTLOOP = 0x01,
        ENABLE_MERGEJOIN = 0x02,
-       ENABLE_HASHJOIN = 0x04
+       ENABLE_HASHJOIN = 0x04,
+       ENABLE_MEMOIZE  = 0x08
 } JOIN_TYPE_BITS;
 
 #define ENABLE_ALL_SCAN (ENABLE_SEQSCAN | ENABLE_INDEXSCAN | \
@@ -158,6 +163,8 @@ typedef enum HintKeyword
        HINT_KEYWORD_SET,
        HINT_KEYWORD_ROWS,
        HINT_KEYWORD_PARALLEL,
+       HINT_KEYWORD_MEMOIZE,
+       HINT_KEYWORD_NOMEMOIZE,
 
        HINT_KEYWORD_UNRECOGNIZED
 } HintKeyword;
@@ -184,7 +191,6 @@ typedef const char *(*HintParseFunction) (Hint *hint, HintState *hstate,
                                                                                  Query *parse, const char *str);
 
 /* hint types */
-#define NUM_HINT_TYPE  6
 typedef enum HintType
 {
        HINT_TYPE_SCAN_METHOD,
@@ -192,7 +198,10 @@ typedef enum HintType
        HINT_TYPE_LEADING,
        HINT_TYPE_SET,
        HINT_TYPE_ROWS,
-       HINT_TYPE_PARALLEL
+       HINT_TYPE_PARALLEL,
+       HINT_TYPE_MEMOIZE,
+
+       NUM_HINT_TYPE
 } HintType;
 
 typedef enum HintTypeBitmap
@@ -229,10 +238,12 @@ static char qnostr[32];
 static const char *current_hint_str = NULL;
 
 /*
- * However we usually take a hint stirng in post_parse_analyze_hook, we still
- * need to do so in planner_hook when client starts query execution from the
- * bind message on a prepared query. This variable prevent duplicate and
- * sometimes harmful hint string retrieval.
+ * We can utilize in-core generated jumble state in post_parse_analyze_hook.
+ * On the other hand there's a case where we're forced to get hints in
+ * planner_hook, where we don't have a jumble state.  If we a query had not a
+ * hint, we need to try to retrieve hints twice or more for one query, which is
+ * the quite common case.  To avoid such case, this variables is set true when
+ * we *try* hint retrieval.
  */
 static bool current_hint_retrieved = false;
 
@@ -362,8 +373,8 @@ struct HintState
        int                             init_min_para_tablescan_size;
        /* min_parallel_index_scan_size*/
        int                             init_min_para_indexscan_size;
-       int                             init_paratup_cost;      /* parallel_tuple_cost */
-       int                             init_parasetup_cost;/* parallel_setup_cost */
+       double                  init_paratup_cost;      /* parallel_tuple_cost */
+       double                  init_parasetup_cost;/* parallel_setup_cost */
 
        PlannerInfo        *current_root;               /* PlannerInfo for the followings */
        Index                   parent_relid;           /* inherit parent of table relid */
@@ -374,11 +385,13 @@ struct HintState
        JoinMethodHint **join_hints;            /* parsed join hints */
        int                             init_join_mask;         /* initial value join parameter */
        List              **join_hint_level;
+       List              **memoize_hint_level;
        LeadingHint       **leading_hint;               /* parsed Leading hints */
        SetHint           **set_hints;                  /* parsed Set hints */
        GucContext              context;                        /* which GUC parameters can we set? */
        RowsHint          **rows_hints;                 /* parsed Rows hints */
        ParallelHint  **parallel_hints;         /* parsed Parallel hints */
+       JoinMethodHint **memoize_hints;         /* parsed Memoize hints */
 };
 
 /*
@@ -391,6 +404,9 @@ typedef struct HintParser
        HintKeyword                     hint_keyword;
 } HintParser;
 
+static bool enable_hint_table_check(bool *newval, void **extra, GucSource source);
+static void assign_enable_hint_table(bool newval, void *extra);
+
 /* Module callbacks */
 void           _PG_init(void);
 void           _PG_fini(void);
@@ -398,13 +414,10 @@ void              _PG_fini(void);
 static void push_hint(HintState *hstate);
 static void pop_hint(void);
 
-static void pg_hint_plan_post_parse_analyze(ParseState *pstate, Query *query);
-static void pg_hint_plan_ProcessUtility(PlannedStmt *pstmt,
-                                       const char *queryString,
-                                       ProcessUtilityContext context,
-                                       ParamListInfo params, QueryEnvironment *queryEnv,
-                                       DestReceiver *dest, char *completionTag);
-static PlannedStmt *pg_hint_plan_planner(Query *parse, int cursorOptions,
+static void pg_hint_plan_post_parse_analyze(ParseState *pstate, Query *query,
+                                                                                       JumbleState *jstate);
+static PlannedStmt *pg_hint_plan_planner(Query *parse, const char *query_string,
+                                                                                int cursorOptions,
                                                                                 ParamListInfo boundParams);
 static RelOptInfo *pg_hint_plan_join_search(PlannerInfo *root,
                                                                                        int levels_needed,
@@ -464,6 +477,9 @@ static int ParallelHintCmp(const ParallelHint *a, const ParallelHint *b);
 static const char *ParallelHintParse(ParallelHint *hint, HintState *hstate,
                                                                         Query *parse, const char *str);
 
+static Hint *MemoizeHintCreate(const char *hint_str, const char *keyword,
+                                                          HintKeyword hint_keyword);
+
 static void quote_value(StringInfo buf, const char *value);
 
 static const char *parse_quoted_value(const char *str, char **word,
@@ -478,15 +494,14 @@ void pg_hint_plan_set_rel_pathlist(PlannerInfo * root, RelOptInfo *rel,
 static void create_plain_partial_paths(PlannerInfo *root,
                                                                                                        RelOptInfo *rel);
 static void make_rels_by_clause_joins(PlannerInfo *root, RelOptInfo *old_rel,
+                                                                         List *other_rels_list,
                                                                          ListCell *other_rels);
 static void make_rels_by_clauseless_joins(PlannerInfo *root,
                                                                                  RelOptInfo *old_rel,
-                                                                                 ListCell *other_rels);
+                                                                                 List *other_rels);
 static bool has_join_restriction(PlannerInfo *root, RelOptInfo *rel);
 static void set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
                                                                   RangeTblEntry *rte);
-static void set_append_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
-                                                                       Index rti, RangeTblEntry *rte);
 RelOptInfo *pg_hint_plan_make_join_rel(PlannerInfo *root, RelOptInfo *rel1,
                                                                           RelOptInfo *rel2);
 
@@ -505,6 +520,8 @@ static void setup_scan_method_enforcement(ScanMethodHint *scanhint,
                                                                                  HintState *state);
 static int set_config_int32_option(const char *name, int32 value,
                                                                        GucContext context);
+static int set_config_double_option(const char *name, double value,
+                                                                       GucContext context);
 
 /* GUC variables */
 static bool    pg_hint_plan_enable_hint = true;
@@ -513,12 +530,16 @@ static int        pg_hint_plan_parse_message_level = INFO;
 static int     pg_hint_plan_debug_message_level = LOG;
 /* Default is off, to keep backward compatibility. */
 static bool    pg_hint_plan_enable_hint_table = false;
+static bool    pg_hint_plan_hints_anywhere = false;
 
 static int plpgsql_recurse_level = 0;          /* PLpgSQL recursion level            */
+static int recurse_level = 0;          /* recursion level incl. direct SPI calls */
 static int hint_inhibit_level = 0;                     /* Inhibit hinting if this is above 0 */
                                                                                        /* (This could not be above 1)        */
 static int max_hint_nworkers = -1;             /* Maximum nworkers of Workers hints */
 
+static bool    hint_table_deactivated = false;
+
 static const struct config_enum_entry parse_messages_level_options[] = {
        {"debug", DEBUG2, true},
        {"debug5", DEBUG5, false},
@@ -559,7 +580,6 @@ static post_parse_analyze_hook_type prev_post_parse_analyze_hook = NULL;
 static planner_hook_type prev_planner = NULL;
 static join_search_hook_type prev_join_search = NULL;
 static set_rel_pathlist_hook_type prev_set_rel_pathlist = NULL;
-static ProcessUtility_hook_type prev_ProcessUtility_hook = NULL;
 
 /* Hold reference to currently active hint */
 static HintState *current_hint_state = NULL;
@@ -599,6 +619,8 @@ static const HintParser parsers[] = {
        {HINT_SET, SetHintCreate, HINT_KEYWORD_SET},
        {HINT_ROWS, RowsHintCreate, HINT_KEYWORD_ROWS},
        {HINT_PARALLEL, ParallelHintCreate, HINT_KEYWORD_PARALLEL},
+       {HINT_MEMOIZE, MemoizeHintCreate, HINT_KEYWORD_MEMOIZE},
+       {HINT_NOMEMOIZE, MemoizeHintCreate, HINT_KEYWORD_NOMEMOIZE},
 
        {NULL, NULL, HINT_KEYWORD_UNRECOGNIZED}
 };
@@ -676,10 +698,23 @@ _PG_init(void)
                                                         false,
                                                         PGC_USERSET,
                                                         0,
+                                                        enable_hint_table_check,
+                                                        assign_enable_hint_table,
+                                                        NULL);
+
+       DefineCustomBoolVariable("pg_hint_plan.hints_anywhere",
+                                                        "Read hints from anywhere in a query.",
+                                                        "This option lets pg_hint_plan ignore syntax so be cautious for false reads.",
+                                                        &pg_hint_plan_hints_anywhere,
+                                                        false,
+                                                        PGC_USERSET,
+                                                        0,
                                                         NULL,
                                                         NULL,
                                                         NULL);
 
+       EmitWarningsOnPlaceholders("pg_hint_plan");
+
        /* Install hooks. */
        prev_post_parse_analyze_hook = post_parse_analyze_hook;
        post_parse_analyze_hook = pg_hint_plan_post_parse_analyze;
@@ -689,8 +724,6 @@ _PG_init(void)
        join_search_hook = pg_hint_plan_join_search;
        prev_set_rel_pathlist = set_rel_pathlist_hook;
        set_rel_pathlist_hook = pg_hint_plan_set_rel_pathlist;
-       prev_ProcessUtility_hook = ProcessUtility_hook;
-       ProcessUtility_hook = pg_hint_plan_ProcessUtility;
 
        /* setup PL/pgSQL plugin hook */
        var_ptr = (PLpgSQL_plugin **) find_rendezvous_variable("PLpgSQL_plugin");
@@ -709,17 +742,40 @@ _PG_fini(void)
        PLpgSQL_plugin  **var_ptr;
 
        /* Uninstall hooks. */
-       post_parse_analyze_hook = prev_post_parse_analyze_hook;
        planner_hook = prev_planner;
        join_search_hook = prev_join_search;
        set_rel_pathlist_hook = prev_set_rel_pathlist;
-       ProcessUtility_hook = prev_ProcessUtility_hook;
 
        /* uninstall PL/pgSQL plugin hook */
        var_ptr = (PLpgSQL_plugin **) find_rendezvous_variable("PLpgSQL_plugin");
        *var_ptr = NULL;
 }
 
+static bool
+enable_hint_table_check(bool *newval, void **extra, GucSource source)
+{
+       if (*newval)
+       {
+               EnableQueryId();
+
+               if (!IsQueryIdEnabled())
+               {
+                       GUC_check_errmsg("table hint is not activated because queryid is not available");
+                       GUC_check_errhint("Set compute_query_id to on or auto to use hint table.");
+                       return false;
+               }
+       }
+
+       return true;
+}
+
+static void
+assign_enable_hint_table(bool newval, void *extra)
+{
+       if (!newval)
+               hint_table_deactivated = false;
+}
+
 /*
  * create and delete functions the hint object
  */
@@ -932,7 +988,7 @@ ParallelHintCreate(const char *hint_str, const char *keyword,
 {
        ParallelHint *hint;
 
-       hint = palloc(sizeof(ScanMethodHint));
+       hint = palloc(sizeof(ParallelHint));
        hint->base.hint_str = hint_str;
        hint->base.keyword = keyword;
        hint->base.hint_keyword = hint_keyword;
@@ -961,6 +1017,23 @@ ParallelHintDelete(ParallelHint *hint)
 }
 
 
+static Hint *
+MemoizeHintCreate(const char *hint_str, const char *keyword,
+                                 HintKeyword hint_keyword)
+{
+       /*
+        * MemoizeHintCreate shares the same struct with JoinMethodHint and the
+        * only difference is the hint type.
+        */
+       JoinMethodHint *hint =
+               (JoinMethodHint *)JoinMethodHintCreate(hint_str, keyword, hint_keyword);
+
+       hint->base.type = HINT_TYPE_MEMOIZE;
+
+       return (Hint *) hint;
+}
+
+
 static HintState *
 HintStateCreate(void)
 {
@@ -987,6 +1060,7 @@ HintStateCreate(void)
        hstate->join_hints = NULL;
        hstate->init_join_mask = 0;
        hstate->join_hint_level = NULL;
+       hstate->memoize_hint_level = NULL;
        hstate->leading_hint = NULL;
        hstate->context = superuser() ? PGC_SUSET : PGC_USERSET;
        hstate->set_hints = NULL;
@@ -1178,7 +1252,8 @@ RowsHintDesc(RowsHint *hint, StringInfo buf, bool nolf)
                        quote_value(buf, hint->relnames[i]);
                }
        }
-       appendStringInfo(buf, " %s", hint->rows_str);
+       if (hint->rows_str != NULL)
+               appendStringInfo(buf, " %s", hint->rows_str);
        appendStringInfoString(buf, ")");
        if (!nolf)
                appendStringInfoChar(buf, '\n');
@@ -1801,114 +1876,6 @@ get_hints_from_table(const char *client_query, const char *client_application)
 }
 
 /*
- * Get client-supplied query string. Addtion to that the jumbled query is
- * supplied if the caller requested. From the restriction of JumbleQuery, some
- * kind of query needs special amendments. Reutrns NULL if this query doesn't
- * change the current hint. This function returns NULL also when something
- * wrong has happend and let the caller continue using the current hints.
- */
-static const char *
-get_query_string(ParseState *pstate, Query *query, Query **jumblequery)
-{
-       const char *p = debug_query_string;
-
-       /*
-        * If debug_query_string is set, it is the top level statement. But in some
-        * cases we reach here with debug_query_string set NULL for example in the
-        * case of DESCRIBE message handling or EXECUTE command. We may still see a
-        * candidate top-level query in pstate in the case.
-        */
-       if (!p && pstate)
-               p = pstate->p_sourcetext;
-
-       /* We don't see a query string, return NULL */
-       if (!p)
-               return NULL;
-
-       if (jumblequery != NULL)
-               *jumblequery = query;
-
-       if (query->commandType == CMD_UTILITY)
-       {
-               Query *target_query = (Query *)query->utilityStmt;
-
-               /*
-                * Some CMD_UTILITY statements have a subquery that we can hint on.
-                * Since EXPLAIN can be placed before other kind of utility statements
-                * and EXECUTE can be contained other kind of utility statements, these
-                * conditions are not mutually exclusive and should be considered in
-                * this order.
-                */
-               if (IsA(target_query, ExplainStmt))
-               {
-                       ExplainStmt *stmt = (ExplainStmt *)target_query;
-                       
-                       Assert(IsA(stmt->query, Query));
-                       target_query = (Query *)stmt->query;
-
-                       /* strip out the top-level query for further processing */
-                       if (target_query->commandType == CMD_UTILITY &&
-                               target_query->utilityStmt != NULL)
-                               target_query = (Query *)target_query->utilityStmt;
-               }
-
-               if (IsA(target_query, DeclareCursorStmt))
-               {
-                       DeclareCursorStmt *stmt = (DeclareCursorStmt *)target_query;
-                       Query *query = (Query *)stmt->query;
-
-                       /* the target must be CMD_SELECT in this case */
-                       Assert(IsA(query, Query) && query->commandType == CMD_SELECT);
-                       target_query = query;
-               }
-
-               if (IsA(target_query, CreateTableAsStmt))
-               {
-                       CreateTableAsStmt  *stmt = (CreateTableAsStmt *) target_query;
-
-                       Assert(IsA(stmt->query, Query));
-                       target_query = (Query *) stmt->query;
-
-                       /* strip out the top-level query for further processing */
-                       if (target_query->commandType == CMD_UTILITY &&
-                               target_query->utilityStmt != NULL)
-                               target_query = (Query *)target_query->utilityStmt;
-               }
-
-               if (IsA(target_query, ExecuteStmt))
-               {
-                       /*
-                        * Use the prepared query for EXECUTE. The Query for jumble
-                        * also replaced with the corresponding one.
-                        */
-                       ExecuteStmt *stmt = (ExecuteStmt *)target_query;
-                       PreparedStatement  *entry;
-
-                       entry = FetchPreparedStatement(stmt->name, true);
-                       p = entry->plansource->query_string;
-                       target_query = (Query *) linitial (entry->plansource->query_list);
-               }
-                       
-               /* JumbleQuery accespts only a non-utility Query */
-               if (!IsA(target_query, Query) ||
-                       target_query->utilityStmt != NULL)
-                       target_query = NULL;
-
-               if (jumblequery)
-                       *jumblequery = target_query;
-       }
-       /*
-        * Return NULL if pstate is not of top-level query.  We don't need this
-        * when jumble info is not requested or cannot do this when pstate is NULL.
-        */
-       else if (!jumblequery && pstate && pstate->p_sourcetext != p &&
-                        strcmp(pstate->p_sourcetext, p) != 0)
-               p = NULL;
-
-       return p;
-}
-
-/*
  * Get hints from the head block comment in client-supplied query string.
  */
 static const char *
@@ -1926,33 +1893,35 @@ get_hints_from_comment(const char *p)
        hint_head = strstr(p, HINT_START);
        if (hint_head == NULL)
                return NULL;
-       for (;p < hint_head; p++)
+       if (!pg_hint_plan_hints_anywhere)
        {
-               /*
-                * Allow these characters precedes hint comment:
-                *   - digits
-                *   - alphabets which are in ASCII range
-                *   - space, tabs and new-lines
-                *   - underscores, for identifier
-                *   - commas, for SELECT clause, EXPLAIN and PREPARE
-                *   - parentheses, for EXPLAIN and PREPARE
-                *
-                * Note that we don't use isalpha() nor isalnum() in ctype.h here to
-                * avoid behavior which depends on locale setting.
-                */
-               if (!(*p >= '0' && *p <= '9') &&
-                       !(*p >= 'A' && *p <= 'Z') &&
-                       !(*p >= 'a' && *p <= 'z') &&
-                       !isspace(*p) &&
-                       *p != '_' &&
-                       *p != ',' &&
-                       *p != '(' && *p != ')')
-                       return NULL;
+               for (;p < hint_head; p++)
+               {
+                       /*
+                        * Allow these characters precedes hint comment:
+                        *   - digits
+                        *   - alphabets which are in ASCII range
+                        *   - space, tabs and new-lines
+                        *   - underscores, for identifier
+                        *   - commas, for SELECT clause, EXPLAIN and PREPARE
+                        *   - parentheses, for EXPLAIN and PREPARE
+                        *
+                        * Note that we don't use isalpha() nor isalnum() in ctype.h here to
+                        * avoid behavior which depends on locale setting.
+                        */
+                       if (!(*p >= '0' && *p <= '9') &&
+                               !(*p >= 'A' && *p <= 'Z') &&
+                               !(*p >= 'a' && *p <= 'z') &&
+                               !isspace(*p) &&
+                               *p != '_' &&
+                               *p != ',' &&
+                               *p != '(' && *p != ')')
+                               return NULL;
+               }
        }
 
-       len = strlen(HINT_START);
-       head = (char *) p;
-       p += len;
+       head = (char *)hint_head;
+       p = head + strlen(HINT_START);
        skip_space(p);
 
        /* find hint end keyword. */
@@ -2062,8 +2031,10 @@ create_hintstate(Query *parse, const char *hints)
                hstate->num_hints[HINT_TYPE_LEADING]);
        hstate->rows_hints = (RowsHint **) (hstate->set_hints +
                hstate->num_hints[HINT_TYPE_SET]);
-       hstate->parallel_hints = (ParallelHint **) (hstate->set_hints +
+       hstate->parallel_hints = (ParallelHint **) (hstate->rows_hints +
                hstate->num_hints[HINT_TYPE_ROWS]);
+       hstate->memoize_hints = (JoinMethodHint **) (hstate->parallel_hints +
+               hstate->num_hints[HINT_TYPE_PARALLEL]);
 
        return hstate;
 }
@@ -2227,6 +2198,10 @@ JoinMethodHintParse(JoinMethodHint *hint, HintState *hstate, Query *parse,
                case HINT_KEYWORD_NOHASHJOIN:
                        hint->enforce_mask = ENABLE_ALL_JOIN ^ ENABLE_HASHJOIN;
                        break;
+               case HINT_KEYWORD_MEMOIZE:
+               case HINT_KEYWORD_NOMEMOIZE:
+                       /* nothing to do here */
+                       break;
                default:
                        hint_ereport(str, ("Unrecognized hint keyword \"%s\".", keyword));
                        return NULL;
@@ -2356,6 +2331,8 @@ RowsHintParse(RowsHint *hint, HintState *hstate, Query *parse,
        List               *name_list = NIL;
        char               *rows_str;
        char               *end_ptr;
+       ListCell   *l;
+       int                     i = 0;
 
        if ((str = parse_parentheses(str, &name_list, hint_keyword)) == NULL)
                return NULL;
@@ -2363,23 +2340,28 @@ RowsHintParse(RowsHint *hint, HintState *hstate, Query *parse,
        /* Last element must be rows specification */
        hint->nrels = list_length(name_list) - 1;
 
-       if (hint->nrels > 0)
+       if (hint->nrels < 1)
        {
-               ListCell   *l;
-               int                     i = 0;
+               hint_ereport(str,
+                                        ("%s hint needs at least one relation followed by one correction term.",
+                                         hint->base.keyword));
+               hint->base.state = HINT_STATE_ERROR;
 
-               /*
-                * Transform relation names from list to array to sort them with qsort
-                * after.
-                */
-               hint->relnames = palloc(sizeof(char *) * hint->nrels);
-               foreach (l, name_list)
-               {
-                       if (hint->nrels <= i)
-                               break;
-                       hint->relnames[i] = lfirst(l);
-                       i++;
-               }
+               return str;
+       }
+       
+
+       /*
+        * Transform relation names from list to array to sort them with qsort
+        * after.
+        */
+       hint->relnames = palloc(sizeof(char *) * hint->nrels);
+       foreach (l, name_list)
+       {
+               if (hint->nrels <= i)
+                       break;
+               hint->relnames[i] = lfirst(l);
+               i++;
        }
 
        /* Retieve rows estimation */
@@ -2478,7 +2460,7 @@ ParallelHintParse(ParallelHint *hint, HintState *hstate, Query *parse,
                                                  hint->base.keyword));
                else if (nworkers < 0)
                        hint_ereport(hint->nworkers_str,
-                                                ("number of workers must be positive: %s",
+                                                ("number of workers must be greater than zero: %s",
                                                  hint->base.keyword));
                else if (nworkers > max_worker_processes)
                        hint_ereport(hint->nworkers_str,
@@ -2548,6 +2530,8 @@ get_current_join_mask()
                mask |= ENABLE_MERGEJOIN;
        if (enable_hashjoin)
                mask |= ENABLE_HASHJOIN;
+       if (enable_memoize)
+               mask |= ENABLE_MEMOIZE;
 
        return mask;
 }
@@ -2613,6 +2597,23 @@ set_config_int32_option(const char *name, int32 value, GucContext context)
                                                                  pg_hint_plan_parse_message_level);
 }
 
+/*
+ * Sets GUC parameter of double type without throwing exceptions. Returns false
+ * if something wrong.
+ */
+static int
+set_config_double_option(const char *name, double value, GucContext context)
+{
+       char *buf = float8out_internal(value);
+       int       result;
+
+       result = set_config_option_noerror(name, buf, context,
+                                                                          PGC_S_SESSION, GUC_ACTION_SAVE, true,
+                                                                          pg_hint_plan_parse_message_level);
+       pfree(buf);
+       return result;
+}
+
 /* setup scan method enforcement according to given options */
 static void
 setup_guc_enforcement(SetHint **options, int noptions, GucContext context)
@@ -2660,8 +2661,8 @@ setup_parallel_plan_enforcement(ParallelHint *hint, HintState *state)
        /* force means that enforce parallel as far as possible */
        if (hint && hint->force_parallel && hint->nworkers > 0)
        {
-               set_config_int32_option("parallel_tuple_cost", 0, state->context);
-               set_config_int32_option("parallel_setup_cost", 0, state->context);
+               set_config_double_option("parallel_tuple_cost", 0.0, state->context);
+               set_config_double_option("parallel_setup_cost", 0.0, state->context);
                set_config_int32_option("min_parallel_table_scan_size", 0,
                                                                state->context);
                set_config_int32_option("min_parallel_index_scan_size", 0,
@@ -2669,9 +2670,9 @@ setup_parallel_plan_enforcement(ParallelHint *hint, HintState *state)
        }
        else
        {
-               set_config_int32_option("parallel_tuple_cost",
+               set_config_double_option("parallel_tuple_cost",
                                                                state->init_paratup_cost, state->context);
-               set_config_int32_option("parallel_setup_cost",
+               set_config_double_option("parallel_setup_cost",
                                                                state->init_parasetup_cost, state->context);
                set_config_int32_option("min_parallel_table_scan_size",
                                                                state->init_min_para_tablescan_size,
@@ -2721,7 +2722,8 @@ setup_scan_method_enforcement(ScanMethodHint *scanhint, HintState *state)
 }
 
 static void
-set_join_config_options(unsigned char enforce_mask, GucContext context)
+set_join_config_options(unsigned char enforce_mask, bool set_memoize,
+                                               GucContext context)
 {
        unsigned char   mask;
 
@@ -2734,6 +2736,34 @@ set_join_config_options(unsigned char enforce_mask, GucContext context)
        SET_CONFIG_OPTION("enable_nestloop", ENABLE_NESTLOOP);
        SET_CONFIG_OPTION("enable_mergejoin", ENABLE_MERGEJOIN);
        SET_CONFIG_OPTION("enable_hashjoin", ENABLE_HASHJOIN);
+
+       if (set_memoize)
+               SET_CONFIG_OPTION("enable_memoize", ENABLE_MEMOIZE);
+
+       /*
+        * Hash join may be rejected for the reason of estimated memory usage. Try
+        * getting rid of that limitation.
+        */
+       if (enforce_mask == ENABLE_HASHJOIN)
+       {
+               char                    buf[32];
+               int                             new_multipler;
+
+               /* See final_cost_hashjoin(). */
+               new_multipler = MAX_KILOBYTES / work_mem;
+
+               /* See guc.c for the upper limit */
+               if (new_multipler >= 1000)
+                       new_multipler = 1000;
+
+               if (new_multipler > hash_mem_multiplier)
+               {
+                       snprintf(buf, sizeof(buf), UINT64_FORMAT, (uint64)new_multipler);
+                       set_config_option_noerror("hash_mem_multiplier", buf,
+                                                                         context, PGC_S_SESSION, GUC_ACTION_SAVE,
+                                                                         true, ERROR);
+               }
+       }
 }
 
 /*
@@ -2774,30 +2804,33 @@ pop_hint(void)
  * Retrieve and store hint string from given query or from the hint table.
  */
 static void
-get_current_hint_string(ParseState *pstate, Query *query)
+get_current_hint_string(Query *query, const char *query_str,
+                                               JumbleState *jstate)
 {
-       const char *query_str;
        MemoryContext   oldcontext;
 
-       /* do nothing under hint table search */
-       if (hint_inhibit_level > 0)
-               return;
+       /* We shouldn't get here for internal queries. */
+       Assert (hint_inhibit_level == 0);
+
+       /* We shouldn't get here if hint is disabled. */
+       Assert (pg_hint_plan_enable_hint);
 
-       /* We alredy have one, don't parse it again. */
+       /* Do not anything if we have already tried to get hints for this query. */
        if (current_hint_retrieved)
                return;
 
+       /* No way to retrieve hints from empty string. */
+       if (!query_str)
+               return;
+
        /* Don't parse the current query hereafter */
        current_hint_retrieved = true;
 
-       if (!pg_hint_plan_enable_hint)
+       /* Make sure trashing old hint string */
+       if (current_hint_str)
        {
-               if (current_hint_str)
-               {
-                       pfree((void *)current_hint_str);
-                       current_hint_str = NULL;
-               }
-               return;
+               pfree((void *)current_hint_str);
+               current_hint_str = NULL;
        }
 
        /* increment the query number */
@@ -2809,119 +2842,100 @@ get_current_hint_string(ParseState *pstate, Query *query)
        /* search the hint table for a hint if requested */
        if (pg_hint_plan_enable_hint_table)
        {
-               int                             query_len;
-               pgssJumbleState jstate;
-               Query              *jumblequery;
-               char               *normalized_query = NULL;
+               int                     query_len;
+               char       *normalized_query;
 
-               query_str = get_query_string(pstate, query, &jumblequery);
-
-               /* If this query is not for hint, just return */
-               if (!query_str)
-                       return;
-
-               /* clear the previous hint string */
-               if (current_hint_str)
-               {
-                       pfree((void *)current_hint_str);
-                       current_hint_str = NULL;
-               }
-               
-               if (jumblequery)
+               if (!IsQueryIdEnabled())
                {
                        /*
-                        * XXX: normalization code is copied from pg_stat_statements.c.
-                        * Make sure to keep up-to-date with it.
+                        * compute_query_id was turned off while enable_hint_table is
+                        * on. Do not go ahead and complain once until it is turned on
+                        * again.
                         */
-                       jstate.jumble = (unsigned char *) palloc(JUMBLE_SIZE);
-                       jstate.jumble_len = 0;
-                       jstate.clocations_buf_size = 32;
-                       jstate.clocations = (pgssLocationLen *)
-                               palloc(jstate.clocations_buf_size * sizeof(pgssLocationLen));
-                       jstate.clocations_count = 0;
+                       if (!hint_table_deactivated)
+                               ereport(WARNING,
+                                               (errmsg ("hint table feature is deactivated because queryid is not available"),
+                                                errhint("Set compute_query_id to \"auto\" or \"on\" to use hint table.")));
 
-                       JumbleQuery(&jstate, jumblequery);
-
-                       /*
-                        * Normalize the query string by replacing constants with '?'
-                        */
-                       /*
-                        * Search hint string which is stored keyed by query string
-                        * and application name.  The query string is normalized to allow
-                        * fuzzy matching.
-                        *
-                        * Adding 1 byte to query_len ensures that the returned string has
-                        * a terminating NULL.
-                        */
-                       query_len = strlen(query_str) + 1;
-                       normalized_query =
-                               generate_normalized_query(&jstate, query_str,
-                                                                                 query->stmt_location,
-                                                                                 &query_len,
-                                                                                 GetDatabaseEncoding());
-
-                       /*
-                        * find a hint for the normalized query. the result should be in
-                        * TopMemoryContext
-                        */
-                       oldcontext = MemoryContextSwitchTo(TopMemoryContext);
-                       current_hint_str =
-                               get_hints_from_table(normalized_query, application_name);
-                       MemoryContextSwitchTo(oldcontext);
+                       hint_table_deactivated = true;
+                       return;
+               }
 
-                       if (debug_level > 1)
-                       {
-                               if (current_hint_str)
-                                       ereport(pg_hint_plan_debug_message_level,
-                                                       (errmsg("pg_hint_plan[qno=0x%x]: "
-                                                                       "post_parse_analyze_hook: "
-                                                                       "hints from table: \"%s\": "
-                                                                       "normalized_query=\"%s\", "
-                                                                       "application name =\"%s\"",
-                                                                       qno, current_hint_str,
-                                                                       normalized_query, application_name),
-                                                        errhidestmt(msgqno != qno),
-                                                        errhidecontext(msgqno != qno)));
-                               else
-                                       ereport(pg_hint_plan_debug_message_level,
-                                                       (errmsg("pg_hint_plan[qno=0x%x]: "
-                                                                       "no match found in table:  "
-                                                                       "application name = \"%s\", "
-                                                                       "normalized_query=\"%s\"",
-                                                                       qno, application_name,
-                                                                       normalized_query),
-                                                        errhidestmt(msgqno != qno),
-                                                        errhidecontext(msgqno != qno)));
-
-                               msgqno = qno;
-                       }
+               if (hint_table_deactivated)
+               {
+                       ereport(LOG, (errmsg ("hint table feature is reactivated")));
+                       hint_table_deactivated = false;
                }
 
-               /* retrun if we have hint here */
-               if (current_hint_str)
+               if (!jstate)
+                       jstate = JumbleQuery(query, query_str);
+
+               if (!jstate)
                        return;
-       }
-       else
-               query_str = get_query_string(pstate, query, NULL);
 
-       if (query_str)
-       {
                /*
-                * get hints from the comment. However we may have the same query
-                * string with the previous call, but the extra comparison seems no
-                * use..
+                * Normalize the query string by replacing constants with '?'
                 */
-               if (current_hint_str)
-                       pfree((void *)current_hint_str);
+               /*
+                * Search hint string which is stored keyed by query string
+                * and application name.  The query string is normalized to allow
+                * fuzzy matching.
+                *
+                * Adding 1 byte to query_len ensures that the returned string has
+                * a terminating NULL.
+                */
+               query_len = strlen(query_str) + 1;
+               normalized_query =
+                       generate_normalized_query(jstate, query_str, 0, &query_len);
 
+               /*
+                * find a hint for the normalized query. the result should be in
+                * TopMemoryContext
+                */
                oldcontext = MemoryContextSwitchTo(TopMemoryContext);
-               current_hint_str = get_hints_from_comment(query_str);
+               current_hint_str =
+                       get_hints_from_table(normalized_query, application_name);
                MemoryContextSwitchTo(oldcontext);
+
+               if (debug_level > 1)
+               {
+                       if (current_hint_str)
+                               ereport(pg_hint_plan_debug_message_level,
+                                               (errmsg("pg_hint_plan[qno=0x%x]: "
+                                                               "hints from table: \"%s\": "
+                                                               "normalized_query=\"%s\", "
+                                                               "application name =\"%s\"",
+                                                               qno, current_hint_str,
+                                                               normalized_query, application_name),
+                                                errhidestmt(msgqno != qno),
+                                                errhidecontext(msgqno != qno)));
+                       else
+                               ereport(pg_hint_plan_debug_message_level,
+                                               (errmsg("pg_hint_plan[qno=0x%x]: "
+                                                               "no match found in table:  "
+                                                               "application name = \"%s\", "
+                                                               "normalized_query=\"%s\"",
+                                                               qno, application_name,
+                                                               normalized_query),
+                                                errhidestmt(msgqno != qno),
+                                                errhidecontext(msgqno != qno)));
+                       
+                       msgqno = qno;
+               }
+
+               /* retrun if we have hint string here */
+               if (current_hint_str)
+                       return;
        }
 
+       /* get hints from the comment */
+       oldcontext = MemoryContextSwitchTo(TopMemoryContext);
+       current_hint_str = get_hints_from_comment(query_str);
+       MemoryContextSwitchTo(oldcontext);
+
        if (debug_level > 1)
        {
-               if (debug_level == 1 && query_str && debug_query_string &&
+               if (debug_level == 2 && query_str && debug_query_string &&
                        strcmp(query_str, debug_query_string))
                        ereport(pg_hint_plan_debug_message_level,
                                        (errmsg("hints in comment=\"%s\"",
@@ -2944,49 +2958,38 @@ get_current_hint_string(ParseState *pstate, Query *query)
  * Retrieve hint string from the current query.
  */
 static void
-pg_hint_plan_post_parse_analyze(ParseState *pstate, Query *query)
+pg_hint_plan_post_parse_analyze(ParseState *pstate, Query *query,
+                                                               JumbleState *jstate)
 {
        if (prev_post_parse_analyze_hook)
-               prev_post_parse_analyze_hook(pstate, query);
+               prev_post_parse_analyze_hook(pstate, query, jstate);
+
+       if (!pg_hint_plan_enable_hint || hint_inhibit_level > 0)
+               return;
 
        /* always retrieve hint from the top-level query string */
        if (plpgsql_recurse_level == 0)
                current_hint_retrieved = false;
 
-       get_current_hint_string(pstate, query);
-}
-
-/*
- * We need to reset current_hint_retrieved flag always when a command execution
- * is finished. This is true even for a pure utility command that doesn't
- * involve planning phase.
- */
-static void
-pg_hint_plan_ProcessUtility(PlannedStmt *pstmt, const char *queryString,
-                                       ProcessUtilityContext context,
-                                       ParamListInfo params, QueryEnvironment *queryEnv,
-                                       DestReceiver *dest, char *completionTag)
-{
-       if (prev_ProcessUtility_hook)
-               prev_ProcessUtility_hook(pstmt, queryString, context, params, queryEnv,
-                                                                dest, completionTag);
-       else
-               standard_ProcessUtility(pstmt, queryString, context, params, queryEnv,
-                                                                dest, completionTag);
-
-       if (plpgsql_recurse_level == 0)
-               current_hint_retrieved = false;
+       /*
+        * Jumble state is required when hint table is used.  This is the only
+        * chance to have one already generated in-core.  If it's not the case, no
+        * use to do the work now and pg_hint_plan_planner() will do the all work.
+        */
+       if (jstate)
+               get_current_hint_string(query, pstate->p_sourcetext, jstate);
 }
 
 /*
  * Read and set up hint information
  */
 static PlannedStmt *
-pg_hint_plan_planner(Query *parse, int cursorOptions, ParamListInfo boundParams)
+pg_hint_plan_planner(Query *parse, const char *query_string, int cursorOptions, ParamListInfo boundParams)
 {
        int                             save_nestlevel;
        PlannedStmt        *result;
        HintState          *hstate;
+       const char         *prev_hint_str = NULL;
 
        /*
         * Use standard planner if pg_hint_plan is disabled or current nesting 
@@ -3008,39 +3011,47 @@ pg_hint_plan_planner(Query *parse, int cursorOptions, ParamListInfo boundParams)
        }
 
        /*
-        * Support for nested plpgsql functions. This is quite ugly but this is the
-        * only point I could find where I can get the query string.
+        * SQL commands invoked in plpgsql functions may also have hints. In that
+        * case override the upper level hint by the new hint.
         */
        if (plpgsql_recurse_level > 0)
        {
-               MemoryContext oldcontext;
+               const char       *tmp_hint_str = current_hint_str;
 
-               if (current_hint_str)
-                       pfree((void *)current_hint_str);
+               /* don't let get_current_hint_string free this string */
+               current_hint_str = NULL;
 
-               oldcontext = MemoryContextSwitchTo(TopMemoryContext);
-               current_hint_str =
-                       get_hints_from_comment((char *)error_context_stack->arg);
-               MemoryContextSwitchTo(oldcontext);
-       }
+               current_hint_retrieved = false;
 
-       /*
-        * Query execution in extended protocol can be started without the analyze
-        * phase. In the case retrieve hint string here.
-        */
-       if (!current_hint_str)
-               get_current_hint_string(NULL, parse);
+               get_current_hint_string(parse, query_string, NULL);
+
+               if (current_hint_str == NULL)
+                       current_hint_str = tmp_hint_str;
+               else if (tmp_hint_str != NULL)
+                       pfree((void *)tmp_hint_str);
+       }
+       else
+               get_current_hint_string(parse, query_string, NULL);
 
-       /* No hint, go the normal way */
+       /* No hints, go the normal way */
        if (!current_hint_str)
                goto standard_planner_proc;
 
        /* parse the hint into hint state struct */
        hstate = create_hintstate(parse, pstrdup(current_hint_str));
 
-       /* run standard planner if the statement has not valid hint */
+       /* run standard planner if we're given with no valid hints */
        if (!hstate)
+       {
+               /* forget invalid hint string */
+               if (current_hint_str)
+               {
+                       pfree((void *)current_hint_str);
+                       current_hint_str = NULL;
+               }
+               
                goto standard_planner_proc;
+       }
        
        /*
         * Push new hint struct to the hint stack to disable previous hint context.
@@ -3082,22 +3093,39 @@ pg_hint_plan_planner(Query *parse, int cursorOptions, ParamListInfo boundParams)
        }
 
        /*
+        * The planner call below may replace current_hint_str. Store and restore
+        * it so that the subsequent planning in the upper level doesn't get
+        * confused.
+        */
+       recurse_level++;
+       prev_hint_str = current_hint_str;
+       current_hint_str = NULL;
+       
+       /*
         * Use PG_TRY mechanism to recover GUC parameters and current_hint_state to
         * the state when this planner started when error occurred in planner.
         */
        PG_TRY();
        {
                if (prev_planner)
-                       result = (*prev_planner) (parse, cursorOptions, boundParams);
+                       result = (*prev_planner) (parse, query_string,
+                                                                         cursorOptions, boundParams);
                else
-                       result = standard_planner(parse, cursorOptions, boundParams);
+                       result = standard_planner(parse, query_string,
+                                                                         cursorOptions, boundParams);
+
+               current_hint_str = prev_hint_str;
+               recurse_level--;
        }
        PG_CATCH();
        {
                /*
                 * Rollback changes of GUC parameters, and pop current hint context
-                * from hint stack to rewind the state.
+                * from hint stack to rewind the state. current_hint_str will be freed
+                * by context deletion.
                 */
+               current_hint_str = prev_hint_str;
+               recurse_level--;
                AtEOXact_GUC(true, save_nestlevel);
                pop_hint();
                PG_RE_THROW();
@@ -3107,13 +3135,13 @@ pg_hint_plan_planner(Query *parse, int cursorOptions, ParamListInfo boundParams)
 
        /*
         * current_hint_str is useless after planning of the top-level query.
+        * There's a case where the caller has multiple queries. This causes hint
+        * parsing multiple times for the same string but we don't have a simple
+        * and reliable way to distinguish that case from the case where of
+        * separate queries.
         */
-       if (plpgsql_recurse_level < 1 && current_hint_str)
-       {
-               pfree((void *)current_hint_str);
-               current_hint_str = NULL;
+       if (recurse_level < 1)
                current_hint_retrieved = false;
-       }
 
        /* Print hint in debug mode. */
        if (debug_level == 1)
@@ -3141,9 +3169,17 @@ standard_planner_proc:
        }
        current_hint_state = NULL;
        if (prev_planner)
-               return (*prev_planner) (parse, cursorOptions, boundParams);
+               result =  (*prev_planner) (parse, query_string,
+                                                                  cursorOptions, boundParams);
        else
-               return standard_planner(parse, cursorOptions, boundParams);
+               result = standard_planner(parse, query_string,
+                                                                 cursorOptions, boundParams);
+
+       /* The upper-level planner still needs the current hint state */
+       if (HintStateStack != NIL)
+               current_hint_state = (HintState *) lfirst(list_head(HintStateStack));
+
+       return result;
 }
 
 /*
@@ -3324,7 +3360,6 @@ restrict_indexes(PlannerInfo *root, ScanMethodHint *hint, RelOptInfo *rel,
                           bool using_parent_hint)
 {
        ListCell           *cell;
-       ListCell           *prev;
        ListCell           *next;
        StringInfoData  buf;
        RangeTblEntry  *rte = root->simple_rte_array[rel->relid];
@@ -3354,7 +3389,6 @@ restrict_indexes(PlannerInfo *root, ScanMethodHint *hint, RelOptInfo *rel,
         * Leaving only an specified index, we delete it from a IndexOptInfo list
         * other than it.
         */
-       prev = NULL;
        if (debug_level > 0)
                initStringInfo(&buf);
 
@@ -3365,8 +3399,7 @@ restrict_indexes(PlannerInfo *root, ScanMethodHint *hint, RelOptInfo *rel,
                ListCell           *l;
                bool                    use_index = false;
 
-               next = lnext(cell);
-
+               next = lnext(rel->indexlist, cell);
                foreach(l, hint->indexnames)
                {
                        char   *hintname = (char *) lfirst(l);
@@ -3536,14 +3569,22 @@ restrict_indexes(PlannerInfo *root, ScanMethodHint *hint, RelOptInfo *rel,
                }
 
                if (!use_index)
-                       rel->indexlist = list_delete_cell(rel->indexlist, cell, prev);
-               else
-                       prev = cell;
+               {
+                       rel->indexlist = list_delete_cell(rel->indexlist, cell);
 
+                       /*
+                        * The cells after the deleted cell have been moved towards the
+                        * list head by 1 element.  the next iteration should visit the
+                        * cell at the same address if any.
+                        */
+                       if (next)
+                               next = cell;
+               }
+                       
                pfree(indexname);
        }
 
-       if (debug_level == 1)
+       if (debug_level > 0)
        {
                StringInfoData  rel_buf;
                char *disprelname = "";
@@ -3719,27 +3760,13 @@ setup_hint_enforcement(PlannerInfo *root, RelOptInfo *rel,
                return 0;
        }
 
-       /* Forget about the parent of another subquery */
-       if (root != current_hint_state->current_root)
-               current_hint_state->parent_relid = 0;
-
-       /* Find the parent for this relation other than the registered parent */
-       foreach (l, root->append_rel_list)
+       if (bms_num_members(rel->top_parent_relids) == 1)
        {
-               AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(l);
-
-               if (appinfo->child_relid == rel->relid)
-               {
-                       if (current_hint_state->parent_relid != appinfo->parent_relid)
-                       {
-                               new_parent_relid = appinfo->parent_relid;
-                               current_hint_state->current_root = root;
-                       }
-                       break;
-               }
+               new_parent_relid = bms_next_member(rel->top_parent_relids, -1);
+               current_hint_state->current_root = root;
+               Assert(new_parent_relid > 0);
        }
-
-       if (!l)
+       else
        {
                /* This relation doesn't have a parent. Cancel current_hint_state. */
                current_hint_state->parent_relid = 0;
@@ -3781,7 +3808,7 @@ setup_hint_enforcement(PlannerInfo *root, RelOptInfo *rel,
 
                                parentrel_oid =
                                        root->simple_rte_array[current_hint_state->parent_relid]->relid;
-                               parent_rel = heap_open(parentrel_oid, NoLock);
+                               parent_rel = table_open(parentrel_oid, NoLock);
 
                                /* Search the parent relation for indexes match the hint spec */
                                foreach(l, RelationGetIndexList(parent_rel))
@@ -3805,7 +3832,7 @@ setup_hint_enforcement(PlannerInfo *root, RelOptInfo *rel,
                                                lappend(current_hint_state->parent_index_infos,
                                                                parent_index_info);
                                }
-                               heap_close(parent_rel, NoLock);
+                               table_close(parent_rel, NoLock);
                        }
                }
        }
@@ -3966,6 +3993,30 @@ find_join_hint(Relids joinrelids)
        return NULL;
 }
 
+
+/*
+ * Return memoize hint which matches given joinrelids.
+ */
+static JoinMethodHint *
+find_memoize_hint(Relids joinrelids)
+{
+       List       *join_hint;
+       ListCell   *l;
+
+       join_hint = current_hint_state->memoize_hint_level[bms_num_members(joinrelids)];
+
+       foreach(l, join_hint)
+       {
+               JoinMethodHint *hint = (JoinMethodHint *) lfirst(l);
+
+               if (bms_equal(joinrelids, hint->joinrelids))
+                       return hint;
+       }
+
+       return NULL;
+}
+
+
 static Relids
 OuterInnerJoinCreate(OuterInnerRels *outer_inner, LeadingHint *leading_hint,
        PlannerInfo *root, List *initial_rels, HintState *hstate, int nbaserel)
@@ -3985,8 +4036,8 @@ OuterInnerJoinCreate(OuterInnerRels *outer_inner, LeadingHint *leading_hint,
                                                                                 leading_hint->base.hint_str));
        }
 
-       outer_rels = lfirst(outer_inner->outer_inner_pair->head);
-       inner_rels = lfirst(outer_inner->outer_inner_pair->tail);
+       outer_rels = linitial(outer_inner->outer_inner_pair);
+       inner_rels = llast(outer_inner->outer_inner_pair);
 
        outer_relids = OuterInnerJoinCreate(outer_rels,
                                                                                leading_hint,
@@ -4121,6 +4172,24 @@ transform_join_hints(HintState *hstate, PlannerInfo *root, int nbaserel,
                        lappend(hstate->join_hint_level[hint->nrels], hint);
        }
 
+       /* ditto for memoize hints */
+       for (i = 0; i < hstate->num_hints[HINT_TYPE_MEMOIZE]; i++)
+       {
+               JoinMethodHint *hint = hstate->join_hints[i];
+
+               if (!hint_state_enabled(hint) || hint->nrels > nbaserel)
+                       continue;
+
+               hint->joinrelids = create_bms_of_relids(&(hint->base), root,
+                                                                        initial_rels, hint->nrels, hint->relnames);
+
+               if (hint->joinrelids == NULL || hint->base.state == HINT_STATE_ERROR)
+                       continue;
+
+               hstate->memoize_hint_level[hint->nrels] =
+                       lappend(hstate->memoize_hint_level[hint->nrels], hint);
+       }
+
        /*
         * Create bitmap of relids from alias names for each rows hint.
         * Bitmaps are more handy than strings in join searching.
@@ -4293,14 +4362,13 @@ transform_join_hints(HintState *hstate, PlannerInfo *root, int nbaserel,
                {
                        if (hstate->join_hint_level[i] != NIL)
                        {
-                               ListCell *prev = NULL;
                                ListCell *next = NULL;
                                for(l = list_head(hstate->join_hint_level[i]); l; l = next)
                                {
 
                                        JoinMethodHint *hint = (JoinMethodHint *)lfirst(l);
 
-                                       next = lnext(l);
+                                       next = lnext(hstate->join_hint_level[i], l);
 
                                        if (hint->inner_nrels == 0 &&
                                                !(bms_intersect(hint->joinrelids, joinrelids) == NULL ||
@@ -4308,11 +4376,16 @@ transform_join_hints(HintState *hstate, PlannerInfo *root, int nbaserel,
                                                  hint->joinrelids)))
                                        {
                                                hstate->join_hint_level[i] =
-                                                       list_delete_cell(hstate->join_hint_level[i], l,
-                                                                                        prev);
+                                                       list_delete_cell(hstate->join_hint_level[i], l);
+                                               /*
+                                                * The cells after the deleted cell have been moved
+                                                * towards the list head by 1 element.  the next
+                                                * iteration should visit the cell at the same address
+                                                * if any.
+                                                */
+                                               if (next)
+                                                       next = l;
                                        }
-                                       else
-                                               prev = l;
                                }
                        }
                }
@@ -4322,7 +4395,8 @@ transform_join_hints(HintState *hstate, PlannerInfo *root, int nbaserel,
 
        if (hint_state_enabled(lhint))
        {
-               set_join_config_options(DISABLE_ALL_JOIN, current_hint_state->context);
+               set_join_config_options(DISABLE_ALL_JOIN, false,
+                                                               current_hint_state->context);
                return true;
        }
        return false;
@@ -4338,34 +4412,57 @@ static RelOptInfo *
 make_join_rel_wrapper(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2)
 {
        Relids                  joinrelids;
-       JoinMethodHint *hint;
+       JoinMethodHint *join_hint;
+       JoinMethodHint *memoize_hint;
        RelOptInfo         *rel;
        int                             save_nestlevel;
 
        joinrelids = bms_union(rel1->relids, rel2->relids);
-       hint = find_join_hint(joinrelids);
+       join_hint = find_join_hint(joinrelids);
+       memoize_hint = find_memoize_hint(joinrelids);
        bms_free(joinrelids);
 
-       if (!hint)
-               return pg_hint_plan_make_join_rel(root, rel1, rel2);
+       /* reject non-matching hints */
+       if (join_hint && join_hint->inner_nrels != 0)
+               join_hint = NULL;
+       
+       if (memoize_hint && memoize_hint->inner_nrels != 0)
+               memoize_hint = NULL;
 
-       if (hint->inner_nrels == 0)
+       if (join_hint || memoize_hint)
        {
                save_nestlevel = NewGUCNestLevel();
 
-               set_join_config_options(hint->enforce_mask,
-                                                               current_hint_state->context);
+               if (join_hint)
+                       set_join_config_options(join_hint->enforce_mask, false,
+                                                                       current_hint_state->context);
 
-               rel = pg_hint_plan_make_join_rel(root, rel1, rel2);
-               hint->base.state = HINT_STATE_USED;
+               if (memoize_hint)
+               {
+                       bool memoize =
+                               memoize_hint->base.hint_keyword == HINT_KEYWORD_MEMOIZE;
+                       set_config_option_noerror("enable_memoize",
+                                                                         memoize ? "true" : "false",
+                                                                         current_hint_state->context,
+                                                                         PGC_S_SESSION, GUC_ACTION_SAVE,
+                                                                         true, ERROR);
+               }
+       }
+
+       /* do the work */
+       rel = pg_hint_plan_make_join_rel(root, rel1, rel2);
+
+       /* Restore the GUC variables we set above. */
+       if (join_hint || memoize_hint)
+       {
+               if (join_hint)
+                       join_hint->base.state = HINT_STATE_USED;
+
+               if (memoize_hint)
+                       memoize_hint->base.state = HINT_STATE_USED;
 
-               /*
-                * Restore the GUC variables we set above.
-                */
                AtEOXact_GUC(true, save_nestlevel);
        }
-       else
-               rel = pg_hint_plan_make_join_rel(root, rel1, rel2);
 
        return rel;
 }
@@ -4384,42 +4481,63 @@ add_paths_to_joinrel_wrapper(PlannerInfo *root,
 {
        Relids                  joinrelids;
        JoinMethodHint *join_hint;
+       JoinMethodHint *memoize_hint;
        int                             save_nestlevel;
 
        joinrelids = bms_union(outerrel->relids, innerrel->relids);
        join_hint = find_join_hint(joinrelids);
+       memoize_hint = find_memoize_hint(joinrelids);
        bms_free(joinrelids);
 
-       if (join_hint && join_hint->inner_nrels != 0)
+       /* reject the found hints if they don't match this join */
+       if (join_hint && join_hint->inner_nrels == 0)
+               join_hint = NULL;
+
+       if (memoize_hint && memoize_hint->inner_nrels == 0)
+               memoize_hint = NULL;
+
+       /* set up configuration if needed */
+       if (join_hint || memoize_hint)
        {
                save_nestlevel = NewGUCNestLevel();
 
-               if (bms_equal(join_hint->inner_joinrelids, innerrel->relids))
+               if (join_hint)
                {
-
-                       set_join_config_options(join_hint->enforce_mask,
-                                                                       current_hint_state->context);
-
-                       add_paths_to_joinrel(root, joinrel, outerrel, innerrel, jointype,
-                                                                sjinfo, restrictlist);
-                       join_hint->base.state = HINT_STATE_USED;
+                       if (bms_equal(join_hint->inner_joinrelids, innerrel->relids))
+                               set_join_config_options(join_hint->enforce_mask, false,
+                                                                               current_hint_state->context);
+                       else
+                               set_join_config_options(DISABLE_ALL_JOIN, false,
+                                                                               current_hint_state->context);
                }
-               else
+
+               if (memoize_hint)
                {
-                       set_join_config_options(DISABLE_ALL_JOIN,
-                                                                       current_hint_state->context);
-                       add_paths_to_joinrel(root, joinrel, outerrel, innerrel, jointype,
-                                                                sjinfo, restrictlist);
+                       bool memoize =
+                               memoize_hint->base.hint_keyword == HINT_KEYWORD_MEMOIZE;
+                       set_config_option_noerror("enable_memoize",
+                                                                         memoize ? "true" : "false",
+                                                                         current_hint_state->context,
+                                                                         PGC_S_SESSION, GUC_ACTION_SAVE,
+                                                                         true, ERROR);
                }
+       }
+
+       /* generate paths */
+       add_paths_to_joinrel(root, joinrel, outerrel, innerrel, jointype,
+                                                sjinfo, restrictlist);
+
+       /* restore GUC variables */
+       if (join_hint || memoize_hint)
+       {
+               if (join_hint)
+                       join_hint->base.state = HINT_STATE_USED;
+
+               if (memoize_hint)
+                       memoize_hint->base.state = HINT_STATE_USED;
 
-               /*
-                * Restore the GUC variables we set above.
-                */
                AtEOXact_GUC(true, save_nestlevel);
        }
-       else
-               add_paths_to_joinrel(root, joinrel, outerrel, innerrel, jointype,
-                                                        sjinfo, restrictlist);
 }
 
 static int
@@ -4482,6 +4600,8 @@ pg_hint_plan_join_search(PlannerInfo *root, int levels_needed,
        current_hint_state->join_hint_level =
                palloc0(sizeof(List *) * (nbaserel + 1));
        join_method_hints = palloc0(sizeof(JoinMethodHint *) * (nbaserel + 1));
+       current_hint_state->memoize_hint_level =
+               palloc0(sizeof(List *) * (nbaserel + 1));
 
        leading_hint_enable = transform_join_hints(current_hint_state,
                                                                                           root, nbaserel,
@@ -4534,7 +4654,7 @@ pg_hint_plan_join_search(PlannerInfo *root, int levels_needed,
        pfree(join_method_hints);
 
        if (leading_hint_enable)
-               set_join_config_options(current_hint_state->init_join_mask,
+               set_join_config_options(current_hint_state->init_join_mask, true,
                                                                current_hint_state->context);
 
        return rel;
@@ -4723,7 +4843,8 @@ pg_hint_plan_set_rel_pathlist(PlannerInfo * root, RelOptInfo *rel,
                                }
 
                                /* Generate gather paths */
-                               if (rel->reloptkind == RELOPT_BASEREL)
+                               if (rel->reloptkind == RELOPT_BASEREL &&
+                                       bms_membership(root->all_baserels) != BMS_SINGLETON)
                                        generate_gather_paths(root, rel, false);
                        }
                }
@@ -4733,58 +4854,6 @@ pg_hint_plan_set_rel_pathlist(PlannerInfo * root, RelOptInfo *rel,
 }
 
 /*
- * set_rel_pathlist
- *       Build access paths for a base relation
- *
- * This function was copied and edited from set_rel_pathlist() in
- * src/backend/optimizer/path/allpaths.c in order not to copy other static
- * functions not required here.
- */
-static void
-set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
-                                Index rti, RangeTblEntry *rte)
-{
-       if (IS_DUMMY_REL(rel))
-       {
-               /* We already proved the relation empty, so nothing more to do */
-       }
-       else if (rte->inh)
-       {
-               /* It's an "append relation", process accordingly */
-               set_append_rel_pathlist(root, rel, rti, rte);
-       }
-       else
-       {
-               if (rel->rtekind == RTE_RELATION)
-               {
-                       if (rte->relkind == RELKIND_RELATION)
-                       {
-                               if(rte->tablesample != NULL)
-                                       elog(ERROR, "sampled relation is not supported");
-
-                               /* Plain relation */
-                               set_plain_rel_pathlist(root, rel, rte);
-                       }
-                       else
-                               elog(ERROR, "unexpected relkind: %c", rte->relkind);
-               }
-               else
-                       elog(ERROR, "unexpected rtekind: %d", (int) rel->rtekind);
-       }
-
-       /*
-        * Allow a plugin to editorialize on the set of Paths for this base
-        * relation.  It could add new paths (such as CustomPaths) by calling
-        * add_path(), or delete or modify paths added by the core code.
-        */
-       if (set_rel_pathlist_hook)
-               (*set_rel_pathlist_hook) (root, rel, rti, rte);
-
-       /* Now find the cheapest of the paths for this rel */
-       set_cheapest(rel);
-}
-
-/*
  * stmt_beg callback is called when each query in PL/pgSQL function is about
  * to be executed.  At that timing, we save query string in the global variable
  * plpgsql_query_string to use it in planner hook.  It's safe to use one global
@@ -4820,6 +4889,14 @@ void plpgsql_query_erase_callback(ResourceReleasePhase phase,
        plpgsql_recurse_level = 0;
 }
 
+
+/* include core static functions */
+static void populate_joinrel_with_paths(PlannerInfo *root, RelOptInfo *rel1,
+                                                                               RelOptInfo *rel2, RelOptInfo *joinrel,
+                                                                               SpecialJoinInfo *sjinfo, List *restrictlist);
+static void set_append_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
+                                                                       Index rti, RangeTblEntry *rte);
+
 #define standard_join_search pg_hint_plan_standard_join_search
 #define join_search_one_level pg_hint_plan_join_search_one_level
 #define make_join_rel make_join_rel_wrapper