OSDN Git Service

Change copyright year to 2020.
[pghintplan/pg_hint_plan.git] / pg_hint_plan.c
index 505ffdf..43ac931 100644 (file)
@@ -3,13 +3,16 @@
  * pg_hint_plan.c
  *               hinting on how to execute a query for PostgreSQL
  *
- * Copyright (c) 2012-2017, NIPPON TELEGRAPH AND TELEPHONE CORPORATION
+ * Copyright (c) 2012-2020, NIPPON TELEGRAPH AND TELEPHONE CORPORATION
  *
  *-------------------------------------------------------------------------
  */
 #include <string.h>
 
 #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"
 #include "parser/analyze.h"
 #include "parser/parsetree.h"
 #include "parser/scansup.h"
+#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"
@@ -91,12 +97,12 @@ PG_MODULE_MAGIC;
 
 #define HINT_ARRAY_DEFAULT_INITSIZE 8
 
-#define hint_ereport(str, detail) \
+#define hint_ereport(str, detail) hint_parse_ereport(str, detail)
+#define hint_parse_ereport(str, detail) \
        do { \
-               ereport(pg_hint_plan_message_level,             \
-                       (errmsg("pg_hint_plan%s: hint syntax error at or near \"%s\"", qnostr, (str)), \
+               ereport(pg_hint_plan_parse_message_level,               \
+                       (errmsg("pg_hint_plan: hint syntax error at or near \"%s\"", (str)), \
                         errdetail detail)); \
-               msgqno = qno; \
        } while(0)
 
 #define skip_space(str) \
@@ -224,6 +230,14 @@ static unsigned int msgqno = 0;
 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.
+ */
+static bool current_hint_retrieved = false;
+
 /* common data for all hints. */
 struct Hint
 {
@@ -350,9 +364,10 @@ 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 */
        ScanMethodHint *parent_scan_hint;       /* scan hint for the parent */
        ParallelHint   *parent_parallel_hint; /* parallel hint for the parent */
@@ -386,6 +401,11 @@ 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,
                                                                                 ParamListInfo boundParams);
 static RelOptInfo *pg_hint_plan_join_search(PlannerInfo *root,
@@ -459,8 +479,6 @@ void pg_hint_plan_set_rel_pathlist(PlannerInfo * root, RelOptInfo *rel,
                                                                   Index rti, RangeTblEntry *rte);
 static void create_plain_partial_paths(PlannerInfo *root,
                                                                                                        RelOptInfo *rel);
-static void add_paths_to_append_rel(PlannerInfo *root, RelOptInfo *rel,
-                                                                       List *live_childrels);
 static void make_rels_by_clause_joins(PlannerInfo *root, RelOptInfo *old_rel,
                                                                          ListCell *other_rels);
 static void make_rels_by_clauseless_joins(PlannerInfo *root,
@@ -471,14 +489,6 @@ 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);
-static void generate_mergeappend_paths(PlannerInfo *root, RelOptInfo *rel,
-                                                                          List *live_childrels,
-                                                                          List *all_child_pathkeys,
-                                                                          List *partitioned_rels);
-static Path *get_cheapest_parameterized_child_path(PlannerInfo *root,
-                                                                         RelOptInfo *rel,
-                                                                         Relids required_outer);
-static List *accumulate_append_subpath(List *subpaths, Path *path);
 RelOptInfo *pg_hint_plan_make_join_rel(PlannerInfo *root, RelOptInfo *rel1,
                                                                           RelOptInfo *rel2);
 
@@ -497,15 +507,19 @@ 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;
 static int debug_level = 0;
-static int     pg_hint_plan_message_level = INFO;
+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 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 */
@@ -550,6 +564,7 @@ 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;
@@ -561,12 +576,6 @@ static HintState *current_hint_state = NULL;
  */
 static List *HintStateStack = NIL;
 
-/*
- * Holds statement name during executing EXECUTE command.  NULL for other
- * statements.
- */
-static char       *stmt_name = NULL;
-
 static const HintParser parsers[] = {
        {HINT_SEQSCAN, ScanMethodHintCreate, HINT_KEYWORD_SEQSCAN},
        {HINT_INDEXSCAN, ScanMethodHintCreate, HINT_KEYWORD_INDEXSCAN},
@@ -644,7 +653,7 @@ _PG_init(void)
        DefineCustomEnumVariable("pg_hint_plan.parse_messages",
                                                         "Message level of parse errors.",
                                                         NULL,
-                                                        &pg_hint_plan_message_level,
+                                                        &pg_hint_plan_parse_message_level,
                                                         INFO,
                                                         parse_messages_level_options,
                                                         PGC_USERSET,
@@ -656,8 +665,8 @@ _PG_init(void)
        DefineCustomEnumVariable("pg_hint_plan.message_level",
                                                         "Message level of debug messages.",
                                                         NULL,
-                                                        &pg_hint_plan_message_level,
-                                                        INFO,
+                                                        &pg_hint_plan_debug_message_level,
+                                                        LOG,
                                                         parse_messages_level_options,
                                                         PGC_USERSET,
                                                         0,
@@ -685,6 +694,8 @@ _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");
@@ -707,6 +718,7 @@ _PG_fini(void)
        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");
@@ -925,7 +937,7 @@ 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;
@@ -972,6 +984,7 @@ HintStateCreate(void)
        hstate->init_min_para_indexscan_size = 0;
        hstate->init_paratup_cost = 0;
        hstate->init_parasetup_cost = 0;
+       hstate->current_root = NULL;
        hstate->parent_relid = 0;
        hstate->parent_scan_hint = NULL;
        hstate->parent_parallel_hint = NULL;
@@ -1170,7 +1183,8 @@ 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');
@@ -1235,7 +1249,7 @@ HintStateDump(HintState *hstate)
 
        if (!hstate)
        {
-               elog(LOG, "pg_hint_plan:\nno hint");
+               elog(pg_hint_plan_debug_message_level, "pg_hint_plan:\nno hint");
                return;
        }
 
@@ -1247,7 +1261,8 @@ HintStateDump(HintState *hstate)
        desc_hint_in_state(hstate, &buf, "duplication hint", HINT_STATE_DUPLICATION, false);
        desc_hint_in_state(hstate, &buf, "error hint", HINT_STATE_ERROR, false);
 
-       elog(LOG, "%s", buf.data);
+       ereport(pg_hint_plan_debug_message_level,
+                       (errmsg ("%s", buf.data)));
 
        pfree(buf.data);
 }
@@ -1259,7 +1274,7 @@ HintStateDump2(HintState *hstate)
 
        if (!hstate)
        {
-               elog(pg_hint_plan_message_level,
+               elog(pg_hint_plan_debug_message_level,
                         "pg_hint_plan%s: HintStateDump: no hint", qnostr);
                return;
        }
@@ -1272,7 +1287,7 @@ HintStateDump2(HintState *hstate)
        desc_hint_in_state(hstate, &buf, "}, {error hints", HINT_STATE_ERROR, true);
        appendStringInfoChar(&buf, '}');
 
-       ereport(pg_hint_plan_message_level,
+       ereport(pg_hint_plan_debug_message_level,
                        (errmsg("%s", buf.data),
                         errhidestmt(true),
                         errhidecontext(true)));
@@ -1655,7 +1670,7 @@ parse_hints(HintState *hstate, Query *parse, const char *str)
                        char   *keyword = parser->keyword;
                        Hint   *hint;
 
-                       if (strcasecmp(buf.data, keyword) != 0)
+                       if (pg_strcasecmp(buf.data, keyword) != 0)
                                continue;
 
                        hint = parser->create_func(head, keyword, parser->hint_keyword);
@@ -1724,7 +1739,7 @@ get_hints_from_table(const char *client_query, const char *client_application)
        char   *hints = NULL;
        Oid             argtypes[2] = { TEXTOID, TEXTOID };
        Datum   values[2];
-       bool    nulls[2] = { false, false };
+       char    nulls[2] = {' ', ' '};
        text   *qry;
        text   *app;
 
@@ -1794,26 +1809,46 @@ 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 the current hint
- * string is still valid.
+ * 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 (pstate && pstate->p_sourcetext)
+               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 *target_query = (Query *)query->utilityStmt;
 
-               /* Use the target query if EXPLAIN */
-               if (IsA(query->utilityStmt, ExplainStmt))
+               /*
+                * 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 *)(query->utilityStmt);
-
+                       ExplainStmt *stmt = (ExplainStmt *)target_query;
+                       
                        Assert(IsA(stmt->query, Query));
                        target_query = (Query *)stmt->query;
 
@@ -1823,53 +1858,68 @@ get_query_string(ParseState *pstate, Query *query, Query **jumblequery)
                                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))
                {
-                       /*
-                        * Use the the body query for CREATE AS. The Query for jumble also
-                        * replaced with the corresponding one.
-                        */
                        CreateTableAsStmt  *stmt = (CreateTableAsStmt *) target_query;
-                       PreparedStatement  *entry;
-                       Query                      *tmp_query;
 
                        Assert(IsA(stmt->query, Query));
-                       tmp_query = (Query *) stmt->query;
+                       target_query = (Query *) stmt->query;
 
-                       if (tmp_query->commandType == CMD_UTILITY &&
-                               IsA(tmp_query->utilityStmt, ExecuteStmt))
-                       {
-                               ExecuteStmt *estmt = (ExecuteStmt *) tmp_query->utilityStmt;
-                               entry = FetchPreparedStatement(estmt->name, true);
-                               p = entry->plansource->query_string;
-                               target_query = (Query *) linitial (entry->plansource->query_list);
-                       }
+                       /* 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;
                }
-               else
+
                if (IsA(target_query, ExecuteStmt))
                {
                        /*
-                        * Use the prepared query for EXECUTE. The Query for jumble also
-                        * replaced with the corresponding one.
+                        * 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);
-               }
 
-               /* We don't accept other than a Query other than a CMD_UTILITY */
-               if (!IsA(target_query, Query) ||
-                       target_query->commandType == CMD_UTILITY)
+                       if (entry->plansource->is_valid)
+                       {
+                               p = entry->plansource->query_string;
+                               target_query = (Query *) linitial (entry->plansource->query_list);
+                       }
+                       else
+                       {
+                               /* igonre the hint for EXECUTE if invalidated */
+                               p = NULL;
+                               target_query = NULL;
+                       }
+               }
+                       
+               /* JumbleQuery accespts only a non-utility Query */
+               if (target_query &&
+                       (!IsA(target_query, Query) ||
+                        target_query->utilityStmt != NULL))
                        target_query = NULL;
 
                if (jumblequery)
                        *jumblequery = target_query;
        }
-       /* Return NULL if the pstate is not identical to the top-level query */
-       else if (strcmp(pstate->p_sourcetext, p) != 0)
+       /*
+        * 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;
@@ -2323,6 +2373,8 @@ 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;
@@ -2330,23 +2382,28 @@ 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 */
@@ -2461,9 +2518,9 @@ ParallelHintParse(ParallelHint *hint, HintState *hstate, Query *parse,
        if (length == 3)
        {
                const char *modeparam = (const char *)list_nth(name_list, 2);
-               if (strcasecmp(modeparam, "hard") == 0)
+               if (pg_strcasecmp(modeparam, "hard") == 0)
                        force_parallel = true;
-               else if (strcasecmp(modeparam, "soft") != 0)
+               else if (pg_strcasecmp(modeparam, "soft") != 0)
                {
                        hint_ereport(modeparam,
                                                 ("enforcement must be soft or hard: %s",
@@ -2569,16 +2626,32 @@ set_config_int32_option(const char *name, int32 value, GucContext context)
 
        if (snprintf(buf, 16, "%d", value) < 0)
        {
-               ereport(pg_hint_plan_message_level,
-                               (errmsg ("Cannot set integer value: %d: %s",
-                                                max_hint_nworkers, strerror(errno))));
+               ereport(pg_hint_plan_parse_message_level,
+                               (errmsg ("Failed to convert integer to string: %d", value)));
                return false;
        }
 
        return
                set_config_option_noerror(name, buf, context,
                                                                  PGC_S_SESSION, GUC_ACTION_SAVE, true,
-                                                                 pg_hint_plan_message_level);
+                                                                 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 */
@@ -2597,7 +2670,7 @@ setup_guc_enforcement(SetHint **options, int noptions, GucContext context)
 
                result = set_config_option_noerror(hint->name, hint->value, context,
                                                                                   PGC_S_SESSION, GUC_ACTION_SAVE, true,
-                                                                                  pg_hint_plan_message_level);
+                                                                                  pg_hint_plan_parse_message_level);
                if (result != 0)
                        hint->base.state = HINT_STATE_USED;
                else
@@ -2626,10 +2699,10 @@ setup_parallel_plan_enforcement(ParallelHint *hint, HintState *state)
                                                                state->init_nworkers, state->context);
 
        /* force means that enforce parallel as far as possible */
-       if (hint && hint->force_parallel)
+       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,
@@ -2637,9 +2710,9 @@ 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,
@@ -2739,24 +2812,25 @@ pop_hint(void)
 }
 
 /*
- * Retrieve and store a hint string from given query or from the hint table.
- * If we are using the hint table, the query string is needed to be normalized.
- * However, ParseState, which is not available in planner_hook, is required to
- * check if the query tree (Query) is surely corresponding to the target query.
+ * Retrieve and store hint string from given query or from the hint table.
  */
 static void
-pg_hint_plan_post_parse_analyze(ParseState *pstate, Query *query)
+get_current_hint_string(ParseState *pstate, Query *query)
 {
        const char *query_str;
        MemoryContext   oldcontext;
 
-       if (prev_post_parse_analyze_hook)
-               prev_post_parse_analyze_hook(pstate, query);
-
        /* do nothing under hint table search */
        if (hint_inhibit_level > 0)
                return;
 
+       /* We alredy have one, don't parse it again. */
+       if (current_hint_retrieved)
+               return;
+
+       /* Don't parse the current query hereafter */
+       current_hint_retrieved = true;
+
        if (!pg_hint_plan_enable_hint)
        {
                if (current_hint_str)
@@ -2797,8 +2871,8 @@ pg_hint_plan_post_parse_analyze(ParseState *pstate, Query *query)
                if (jumblequery)
                {
                        /*
-                        * XXX: normalizing code is copied from pg_stat_statements.c, so be
-                        * careful to PostgreSQL's version up.
+                        * XXX: normalization code is copied from pg_stat_statements.c.
+                        * Make sure to keep up-to-date with it.
                         */
                        jstate.jumble = (unsigned char *) palloc(JUMBLE_SIZE);
                        jstate.jumble_len = 0;
@@ -2822,8 +2896,7 @@ pg_hint_plan_post_parse_analyze(ParseState *pstate, Query *query)
                         */
                        query_len = strlen(query_str) + 1;
                        normalized_query =
-                               generate_normalized_query(&jstate, query_str,
-                                                                                 &query_len,
+                               generate_normalized_query(&jstate, query_str, 0, &query_len,
                                                                                  GetDatabaseEncoding());
 
                        /*
@@ -2838,7 +2911,7 @@ pg_hint_plan_post_parse_analyze(ParseState *pstate, Query *query)
                        if (debug_level > 1)
                        {
                                if (current_hint_str)
-                                       ereport(pg_hint_plan_message_level,
+                                       ereport(pg_hint_plan_debug_message_level,
                                                        (errmsg("pg_hint_plan[qno=0x%x]: "
                                                                        "post_parse_analyze_hook: "
                                                                        "hints from table: \"%s\": "
@@ -2849,7 +2922,7 @@ pg_hint_plan_post_parse_analyze(ParseState *pstate, Query *query)
                                                         errhidestmt(msgqno != qno),
                                                         errhidecontext(msgqno != qno)));
                                else
-                                       ereport(pg_hint_plan_message_level,
+                                       ereport(pg_hint_plan_debug_message_level,
                                                        (errmsg("pg_hint_plan[qno=0x%x]: "
                                                                        "no match found in table:  "
                                                                        "application name = \"%s\", "
@@ -2863,7 +2936,7 @@ pg_hint_plan_post_parse_analyze(ParseState *pstate, Query *query)
                        }
                }
 
-               /* retrun if we have hint here*/
+               /* retrun if we have hint here */
                if (current_hint_str)
                        return;
        }
@@ -2874,8 +2947,8 @@ pg_hint_plan_post_parse_analyze(ParseState *pstate, Query *query)
        {
                /*
                 * get hints from the comment. However we may have the same query
-                * string with the previous call, but just retrieving hints is expected
-                * to be faster than checking for identicalness before retrieval.
+                * string with the previous call, but the extra comparison seems no
+                * use..
                 */
                if (current_hint_str)
                        pfree((void *)current_hint_str);
@@ -2884,21 +2957,30 @@ pg_hint_plan_post_parse_analyze(ParseState *pstate, Query *query)
                current_hint_str = get_hints_from_comment(query_str);
                MemoryContextSwitchTo(oldcontext);
        }
+       else
+       {
+               /*
+                * Failed to get query. We would be in fetching invalidated
+                * plancache. Try the next chance.
+                */
+               current_hint_retrieved = false;
+       }
 
        if (debug_level > 1)
        {
-               if (debug_level == 1 &&
-                       (stmt_name || strcmp(query_str, debug_query_string)))
-                       ereport(pg_hint_plan_message_level,
+               if (debug_level == 1 && query_str && debug_query_string &&
+                       strcmp(query_str, debug_query_string))
+                       ereport(pg_hint_plan_debug_message_level,
                                        (errmsg("hints in comment=\"%s\"",
                                                        current_hint_str ? current_hint_str : "(none)"),
                                         errhidestmt(msgqno != qno),
                                         errhidecontext(msgqno != qno)));
                else
-                       ereport(pg_hint_plan_message_level,
-                                       (errmsg("hints in comment=\"%s\", stmt=\"%s\", query=\"%s\", debug_query_string=\"%s\"",
+                       ereport(pg_hint_plan_debug_message_level,
+                                       (errmsg("hints in comment=\"%s\", query=\"%s\", debug_query_string=\"%s\"",
                                                        current_hint_str ? current_hint_str : "(none)",
-                                                       stmt_name, query_str, debug_query_string),
+                                                       query_str ? query_str : "(none)",
+                                                       debug_query_string ? debug_query_string : "(none)"),
                                         errhidestmt(msgqno != qno),
                                         errhidecontext(msgqno != qno)));
                msgqno = qno;
@@ -2906,6 +2988,44 @@ pg_hint_plan_post_parse_analyze(ParseState *pstate, Query *query)
 }
 
 /*
+ * Retrieve hint string from the current query.
+ */
+static void
+pg_hint_plan_post_parse_analyze(ParseState *pstate, Query *query)
+{
+       if (prev_post_parse_analyze_hook)
+               prev_post_parse_analyze_hook(pstate, query);
+
+       /* 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;
+}
+
+/*
  * Read and set up hint information
  */
 static PlannedStmt *
@@ -2914,6 +3034,7 @@ pg_hint_plan_planner(Query *parse, 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 
@@ -2923,7 +3044,7 @@ pg_hint_plan_planner(Query *parse, int cursorOptions, ParamListInfo boundParams)
        if (!pg_hint_plan_enable_hint || hint_inhibit_level > 0)
        {
                if (debug_level > 1)
-                       ereport(pg_hint_plan_message_level,
+                       ereport(pg_hint_plan_debug_message_level,
                                        (errmsg ("pg_hint_plan%s: planner: enable_hint=%d,"
                                                         " hint_inhibit_level=%d",
                                                         qnostr, pg_hint_plan_enable_hint,
@@ -2938,19 +3059,25 @@ 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.
         */
-       if (plpgsql_recurse_level > 0)
+       if (plpgsql_recurse_level > 0 &&
+               error_context_stack && error_context_stack->arg)
        {
                MemoryContext oldcontext;
 
-               if (current_hint_str)
-                       pfree((void *)current_hint_str);
-
                oldcontext = MemoryContextSwitchTo(TopMemoryContext);
                current_hint_str =
                        get_hints_from_comment((char *)error_context_stack->arg);
                MemoryContextSwitchTo(oldcontext);
        }
 
+       /*
+        * 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);
+
+       /* No hint, go the normal way */
        if (!current_hint_str)
                goto standard_planner_proc;
 
@@ -2994,13 +3121,22 @@ pg_hint_plan_planner(Query *parse, int cursorOptions, ParamListInfo boundParams)
 
        if (debug_level > 1)
        {
-               ereport(pg_hint_plan_message_level,
+               ereport(pg_hint_plan_debug_message_level,
                                (errhidestmt(msgqno != qno),
                                 errmsg("pg_hint_plan%s: planner", qnostr))); 
                msgqno = qno;
        }
 
        /*
+        * 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.
         */
@@ -3010,6 +3146,9 @@ pg_hint_plan_planner(Query *parse, int cursorOptions, ParamListInfo boundParams)
                        result = (*prev_planner) (parse, cursorOptions, boundParams);
                else
                        result = standard_planner(parse, cursorOptions, boundParams);
+
+               current_hint_str = prev_hint_str;
+               recurse_level--;
        }
        PG_CATCH();
        {
@@ -3017,12 +3156,25 @@ pg_hint_plan_planner(Query *parse, int cursorOptions, ParamListInfo boundParams)
                 * Rollback changes of GUC parameters, and pop current hint context
                 * from hint stack to rewind the state.
                 */
+               current_hint_str = prev_hint_str;
+               recurse_level--;
                AtEOXact_GUC(true, save_nestlevel);
                pop_hint();
                PG_RE_THROW();
        }
        PG_END_TRY();
 
+
+       /*
+        * current_hint_str is useless after planning of the top-level query.
+        */
+       if (recurse_level < 1 && current_hint_str)
+       {
+               pfree((void *)current_hint_str);
+               current_hint_str = NULL;
+               current_hint_retrieved = false;
+       }
+
        /* Print hint in debug mode. */
        if (debug_level == 1)
                HintStateDump(current_hint_state);
@@ -3041,7 +3193,7 @@ pg_hint_plan_planner(Query *parse, int cursorOptions, ParamListInfo boundParams)
 standard_planner_proc:
        if (debug_level > 1)
        {
-               ereport(pg_hint_plan_message_level,
+               ereport(pg_hint_plan_debug_message_level,
                                (errhidestmt(msgqno != qno),
                                 errmsg("pg_hint_plan%s: planner: no valid hint",
                                                qnostr)));
@@ -3049,9 +3201,15 @@ standard_planner_proc:
        }
        current_hint_state = NULL;
        if (prev_planner)
-               return (*prev_planner) (parse, cursorOptions, boundParams);
+               result =  (*prev_planner) (parse, cursorOptions, boundParams);
        else
-               return standard_planner(parse, cursorOptions, boundParams);
+               result = standard_planner(parse, 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;
 }
 
 /*
@@ -3340,7 +3498,7 @@ restrict_indexes(PlannerInfo *root, ScanMethodHint *hint, RelOptInfo *rel,
                                                break;
 
                                        c_attname = get_attname(relationObjectId,
-                                                                                               info->indexkeys[i]);
+                                                                                       info->indexkeys[i], false);
 
                                        /* deny if any of column attributes don't match */
                                        if (strcmp(p_attname, c_attname) != 0 ||
@@ -3367,7 +3525,7 @@ restrict_indexes(PlannerInfo *root, ScanMethodHint *hint, RelOptInfo *rel,
 
                                        /* check expressions if both expressions are available */
                                        if (p_info->expression_str &&
-                                               !heap_attisnull(ht_idx, Anum_pg_index_indexprs))
+                                               !heap_attisnull(ht_idx, Anum_pg_index_indexprs, NULL))
                                        {
                                                Datum       exprsDatum;
                                                bool        isnull;
@@ -3398,7 +3556,7 @@ restrict_indexes(PlannerInfo *root, ScanMethodHint *hint, RelOptInfo *rel,
 
                                        /* compare index predicates  */
                                        if (p_info->indpred_str &&
-                                               !heap_attisnull(ht_idx, Anum_pg_index_indpred))
+                                               !heap_attisnull(ht_idx, Anum_pg_index_indpred, NULL))
                                        {
                                                Datum       predDatum;
                                                bool        isnull;
@@ -3469,7 +3627,7 @@ restrict_indexes(PlannerInfo *root, ScanMethodHint *hint, RelOptInfo *rel,
                initStringInfo(&rel_buf);
                quote_value(&rel_buf, disprelname);
 
-               ereport(LOG,
+               ereport(pg_hint_plan_debug_message_level,
                                (errmsg("available indexes for %s(%s):%s",
                                         hint->base.keyword,
                                         rel_buf.data,
@@ -3503,9 +3661,14 @@ get_parent_index_info(Oid indexoid, Oid relid)
        p_info->opclass = (Oid *) palloc(sizeof(Oid) * index->indnatts);
        p_info->indoption = (int16 *) palloc(sizeof(Oid) * index->indnatts);
 
+       /*
+        * Collect relation attribute names of index columns for index
+        * identification, not index attribute names. NULL means expression index
+        * columns.
+        */
        for (i = 0; i < index->indnatts; i++)
        {
-               attname = get_attname(relid, index->indkey.values[i]);
+               attname = get_attname(relid, index->indkey.values[i], true);
                p_info->column_names = lappend(p_info->column_names, attname);
 
                p_info->indcollation[i] = indexRelation->rd_indcollation[i];
@@ -3517,7 +3680,8 @@ get_parent_index_info(Oid indexoid, Oid relid)
         * to check to match the expression's parameter of index with child indexes
         */
        p_info->expression_str = NULL;
-       if(!heap_attisnull(indexRelation->rd_indextuple, Anum_pg_index_indexprs))
+       if(!heap_attisnull(indexRelation->rd_indextuple, Anum_pg_index_indexprs,
+                                          NULL))
        {
                Datum       exprsDatum;
                bool            isnull;
@@ -3537,7 +3701,8 @@ get_parent_index_info(Oid indexoid, Oid relid)
         * to check to match the predicate's parameter of index with child indexes
         */
        p_info->indpred_str = NULL;
-       if(!heap_attisnull(indexRelation->rd_indextuple, Anum_pg_index_indpred))
+       if(!heap_attisnull(indexRelation->rd_indextuple, Anum_pg_index_indpred,
+                                          NULL))
        {
                Datum       predDatum;
                bool            isnull;
@@ -3573,7 +3738,7 @@ reset_hint_enforcement()
  * bitmap of HintTypeBitmap. If shint or phint is not NULL, set used hint
  * there respectively.
  */
-static bool
+static int
 setup_hint_enforcement(PlannerInfo *root, RelOptInfo *rel,
                                           ScanMethodHint **rshint, ParallelHint **rphint)
 {
@@ -3598,8 +3763,18 @@ setup_hint_enforcement(PlannerInfo *root, RelOptInfo *rel,
         */
        if (inhparent)
        {
+               /* set up only parallel hints for parent relation */
+               phint = find_parallel_hint(root, rel->relid);
+               if (phint)
+               {
+                       setup_parallel_plan_enforcement(phint, current_hint_state);
+                       if (rphint) *rphint = phint;
+                       ret |= HINT_BM_PARALLEL;
+                       return ret;
+               }
+
                if (debug_level > 1)
-                       ereport(pg_hint_plan_message_level,
+                       ereport(pg_hint_plan_debug_message_level,
                                        (errhidestmt(true),
                                         errmsg ("pg_hint_plan%s: setup_hint_enforcement"
                                                         " skipping inh parent: relation=%u(%s), inhparent=%d,"
@@ -3610,33 +3785,58 @@ setup_hint_enforcement(PlannerInfo *root, RelOptInfo *rel,
                return 0;
        }
 
-       /* Find the parent for this relation other than the registered parent */
-       foreach (l, root->append_rel_list)
+       /*
+        * Forget about the parent of another subquery, but don't forget if the
+        * inhTargetkind of the root is not INHKIND_NONE, which signals the root
+        * contains only appendrel members. See inheritance_planner for details.
+        *
+        * (PG12.0) 428b260f87 added one more planning cycle for updates on
+        * partitioned tables and hints set up in the cycle are overriden by the
+        * second cycle. Since I didn't find no apparent distinction between the
+        * PlannerRoot of the cycle and that of ordinary CMD_SELECT, pg_hint_plan
+        * accepts both cycles and the later one wins. In the second cycle root
+        * doesn't have inheritance information at all so use the parent_relid set
+        * in the first cycle.
+        */
+       if (root->inhTargetKind == INHKIND_NONE)
        {
-               AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(l);
+               if (root != current_hint_state->current_root)
+                       current_hint_state->parent_relid = 0;
 
-               if (appinfo->child_relid == rel->relid)
+               /* Find the parent for this relation other than the registered parent */
+               foreach (l, root->append_rel_list)
                {
-                       if (current_hint_state->parent_relid != appinfo->parent_relid)
-                               new_parent_relid = appinfo->parent_relid;
-                       break;
+                       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;
+                       }
                }
-       }
 
-       if (!l)
-       {
-               /* This relation doesn't have a parent. Cancel current_hint_state. */
-               current_hint_state->parent_relid = 0;
-               current_hint_state->parent_scan_hint = NULL;
-               current_hint_state->parent_parallel_hint = NULL;
+               if (!l)
+               {
+                       /*
+                        * This relation doesn't have a parent. Cancel
+                        * current_hint_state.
+                        */
+                       current_hint_state->parent_relid = 0;
+                       current_hint_state->parent_scan_hint = NULL;
+                       current_hint_state->parent_parallel_hint = NULL;
+               }
        }
 
        if (new_parent_relid > 0)
        {
                /*
                 * Here we found a new parent for the current relation. Scan continues
-                * hint to other childrens of this parent so remember it to avoid
-                * hinthintredundant setup cost.
+                * hint to other childrens of this parent so remember it to avoid
+                * redundant setup cost.
                 */
                current_hint_state->parent_relid = new_parent_relid;
                                
@@ -3718,7 +3918,7 @@ setup_hint_enforcement(PlannerInfo *root, RelOptInfo *rel,
                        if (shint == current_hint_state->parent_scan_hint)
                                additional_message = " by parent hint";
 
-                       ereport(pg_hint_plan_message_level,
+                       ereport(pg_hint_plan_debug_message_level,
                                        (errhidestmt(true),
                                         errmsg ("pg_hint_plan%s: setup_hint_enforcement"
                                                         " index deletion%s:"
@@ -3748,7 +3948,7 @@ setup_hint_enforcement(PlannerInfo *root, RelOptInfo *rel,
        if (!shint && ! phint)
        {
                if (debug_level > 1)
-                       ereport(pg_hint_plan_message_level,
+                       ereport(pg_hint_plan_debug_message_level,
                                        (errhidestmt (true),
                                         errmsg ("pg_hint_plan%s: setup_hint_enforcement"
                                                         " no hint applied:"
@@ -4373,6 +4573,38 @@ pg_hint_plan_join_search(PlannerInfo *root, int levels_needed,
 
        rel = pg_hint_plan_standard_join_search(root, levels_needed, initial_rels);
 
+       /*
+        * Adjust number of parallel workers of the result rel to the largest
+        * number of the component paths.
+        */
+       if (current_hint_state->num_hints[HINT_TYPE_PARALLEL] > 0)
+       {
+               ListCell   *lc;
+               int             nworkers = 0;
+       
+               foreach (lc, initial_rels)
+               {
+                       ListCell *lcp;
+                       RelOptInfo *rel = (RelOptInfo *) lfirst(lc);
+
+                       foreach (lcp, rel->partial_pathlist)
+                       {
+                               Path *path = (Path *) lfirst(lcp);
+
+                               if (nworkers < path-> parallel_workers)
+                                       nworkers = path-> parallel_workers;
+                       }
+               }
+
+               foreach (lc, rel->partial_pathlist)
+               {
+                       Path *path = (Path *) lfirst(lc);
+
+                       if (path->parallel_safe && path->parallel_workers < nworkers)
+                               path->parallel_workers = nworkers;
+               }
+       }
+
        for (i = 2; i <= nbaserel; i++)
        {
                list_free(current_hint_state->join_hint_level[i]);
@@ -4419,11 +4651,65 @@ pg_hint_plan_set_rel_pathlist(PlannerInfo * root, RelOptInfo *rel,
         * We can accept only plain relations, foreign tables and table saples are
         * also unacceptable. See set_rel_pathlist.
         */
-       if (rel->rtekind != RTE_RELATION ||
+       if ((rel->rtekind != RTE_RELATION &&
+                rel->rtekind != RTE_SUBQUERY)||
                rte->relkind == RELKIND_FOREIGN_TABLE ||
                rte->tablesample != NULL)
                return;
 
+       /*
+        * Even though UNION ALL node doesn't have particular name so usually it is
+        * unhintable, turn on parallel when it contains parallel nodes.
+        */
+       if (rel->rtekind == RTE_SUBQUERY)
+       {
+               ListCell *lc;
+               bool    inhibit_nonparallel = false;
+
+               if (rel->partial_pathlist == NIL)
+                       return;
+
+               foreach(lc, rel->partial_pathlist)
+               {
+                       ListCell *lcp;
+                       AppendPath *apath = (AppendPath *) lfirst(lc);
+                       int             parallel_workers = 0;
+
+                       if (!IsA(apath, AppendPath))
+                               continue;
+
+                       foreach (lcp, apath->subpaths)
+                       {
+                               Path *spath = (Path *) lfirst(lcp);
+
+                               if (spath->parallel_aware &&
+                                       parallel_workers < spath->parallel_workers)
+                                       parallel_workers = spath->parallel_workers;
+                       }
+
+                       apath->path.parallel_workers = parallel_workers;
+                       inhibit_nonparallel = true;
+               }
+
+               if (inhibit_nonparallel)
+               {
+                       ListCell *lc;
+
+                       foreach(lc, rel->pathlist)
+                       {
+                               Path *path = (Path *) lfirst(lc);
+
+                               if (path->startup_cost < disable_cost)
+                               {
+                                       path->startup_cost += disable_cost;
+                                       path->total_cost += disable_cost;
+                               }
+                       }
+               }
+
+               return;
+       }
+
        /* We cannot handle if this requires an outer */
        if (rel->lateral_relids)
                return;
@@ -4435,49 +4721,96 @@ pg_hint_plan_set_rel_pathlist(PlannerInfo * root, RelOptInfo *rel,
        /* Here, we regenerate paths with the current hint restriction */
        if (found_hints & HINT_BM_SCAN_METHOD || found_hints & HINT_BM_PARALLEL)
        {
-               /* Just discard all the paths considered so far */
-               list_free_deep(rel->pathlist);
-               rel->pathlist = NIL;
+               /*
+                * When hint is specified on non-parent relations, discard existing
+                * paths and regenerate based on the hint considered. Otherwise we
+                * already have hinted childx paths then just adjust the number of
+                * planned number of workers.
+                */
+               if (root->simple_rte_array[rel->relid]->inh)
+               {
+                       /* enforce number of workers if requested */
+                       if (phint && phint->force_parallel)
+                       {
+                               if (phint->nworkers == 0)
+                               {
+                                       list_free_deep(rel->partial_pathlist);
+                                       rel->partial_pathlist = NIL;
+                               }
+                               else
+                               {
+                                       /* prioritize partial paths */
+                                       foreach (l, rel->partial_pathlist)
+                                       {
+                                               Path *ppath = (Path *) lfirst(l);
 
-               /* Remove all the partial paths if Parallel hint is specfied */
-               if ((found_hints & HINT_BM_PARALLEL) && rel->partial_pathlist)
+                                               if (ppath->parallel_safe)
+                                               {
+                                                       ppath->parallel_workers = phint->nworkers;
+                                                       ppath->startup_cost = 0;
+                                                       ppath->total_cost = 0;
+                                               }
+                                       }
+
+                                       /* disable non-partial paths */
+                                       foreach (l, rel->pathlist)
+                                       {
+                                               Path *ppath = (Path *) lfirst(l);
+
+                                               if (ppath->startup_cost < disable_cost)
+                                               {
+                                                       ppath->startup_cost += disable_cost;
+                                                       ppath->total_cost += disable_cost;
+                                               }
+                                       }
+                               }
+                       }
+               }
+               else
                {
+                       /* Just discard all the paths considered so far */
+                       list_free_deep(rel->pathlist);
+                       rel->pathlist = NIL;
                        list_free_deep(rel->partial_pathlist);
                        rel->partial_pathlist = NIL;
-               }
 
-               /* Regenerate paths with the current enforcement */
-               set_plain_rel_pathlist(root, rel, rte);
+                       /* Regenerate paths with the current enforcement */
+                       set_plain_rel_pathlist(root, rel, rte);
 
-               /* Additional work to enforce parallel query execution */
-               if (phint && phint->nworkers > 0)
-               {
-                       /* Lower the priorities of non-parallel paths */
-                       foreach (l, rel->pathlist)
+                       /* Additional work to enforce parallel query execution */
+                       if (phint && phint->nworkers > 0)
                        {
-                               Path *path = (Path *) lfirst(l);
-
-                               if (path->startup_cost < disable_cost)
+                               /*
+                                * For Parallel Append to be planned properly, we shouldn't set
+                                * the costs of non-partial paths to disable-value.  Lower the
+                                * priority of non-parallel paths by setting partial path costs
+                                * to 0 instead.
+                                */
+                               foreach (l, rel->partial_pathlist)
                                {
-                                       path->startup_cost += disable_cost;
-                                       path->total_cost += disable_cost;
+                                       Path *path = (Path *) lfirst(l);
+
+                                       path->startup_cost = 0;
+                                       path->total_cost = 0;
                                }
-                       }
 
-                       /* enforce number of workers if requested */
-                       if (phint->force_parallel)
-                       {
-                               foreach (l, rel->partial_pathlist)
+                               /* enforce number of workers if requested */
+                               if (phint->force_parallel)
                                {
-                                       Path *ppath = (Path *) lfirst(l);
+                                       foreach (l, rel->partial_pathlist)
+                                       {
+                                               Path *ppath = (Path *) lfirst(l);
 
-                                       ppath->parallel_workers = phint->nworkers;
+                                               if (ppath->parallel_safe)
+                                                       ppath->parallel_workers = phint->nworkers;
+                                       }
                                }
-                       }
 
-                       /* Generate gather paths for base rels */
-                       if (rel->reloptkind == RELOPT_BASEREL)
-                               generate_gather_paths(root, rel);
+                               /* Generate gather paths */
+                               if (rel->reloptkind == RELOPT_BASEREL &&
+                                       bms_membership(root->all_baserels) != BMS_SINGLETON)
+                                       generate_gather_paths(root, rel, false);
+                       }
                }
        }
 
@@ -4566,7 +4899,7 @@ void plpgsql_query_erase_callback(ResourceReleasePhase phase,
                                                                  bool isTopLevel,
                                                                  void *arg)
 {
-       if (phase != RESOURCE_RELEASE_AFTER_LOCKS)
+       if (!isTopLevel || phase != RESOURCE_RELEASE_AFTER_LOCKS)
                return;
        /* Cancel plpgsql nest level*/
        plpgsql_recurse_level = 0;