Improve comments.

Also arrange the hint keywords in same order as parser definition.

diff --git a/pg_hint_plan.c b/pg_hint_plan.c
index b818b67..fc093b0 100644 (file)
--- a/pg_hint_plan.c
+++ b/pg_hint_plan.c
@@ -31,27 +31,27 @@ PG_MODULE_MAGIC;
 #define HINT_END       "*/"
 
 /* hint keywords */
-#define HINT_SEQSCAN           "SeqScan"
-#define HINT_INDEXSCAN         "IndexScan"
-#define HINT_BITMAPSCAN                "BitmapScan"
-#define HINT_TIDSCAN           "TidScan"
-#define HINT_NOSEQSCAN         "NoSeqScan"
-#define HINT_NOINDEXSCAN       "NoIndexScan"
-#define HINT_NOBITMAPSCAN      "NoBitmapScan"
-#define HINT_NOTIDSCAN         "NoTidScan"
-#define HINT_NESTLOOP          "NestLoop"
-#define HINT_MERGEJOIN         "MergeJoin"
-#define HINT_HASHJOIN          "HashJoin"
-#define HINT_NONESTLOOP                "NoNestLoop"
-#define HINT_NOMERGEJOIN       "NoMergeJoin"
-#define HINT_NOHASHJOIN                "NoHashJoin"
-#define HINT_LEADING           "Leading"
-#define HINT_SET                       "Set"
-
+#define HINT_SEQSCAN                   "SeqScan"
+#define HINT_INDEXSCAN                 "IndexScan"
+#define HINT_BITMAPSCAN                        "BitmapScan"
+#define HINT_TIDSCAN                   "TidScan"
+#define HINT_NOSEQSCAN                 "NoSeqScan"
+#define HINT_NOINDEXSCAN               "NoIndexScan"
+#define HINT_NOBITMAPSCAN              "NoBitmapScan"
+#define HINT_NOTIDSCAN                 "NoTidScan"
 #if PG_VERSION_NUM >= 90200
-#define        HINT_INDEXONLYSCAN              "IndexonlyScan"
-#define        HINT_NOINDEXONLYSCAN    "NoIndexonlyScan"
+#define HINT_INDEXONLYSCAN             "IndexonlyScan"
+#define HINT_NOINDEXONLYSCAN   "NoIndexonlyScan"
 #endif
+#define HINT_NESTLOOP                  "NestLoop"
+#define HINT_MERGEJOIN                 "MergeJoin"
+#define HINT_HASHJOIN                  "HashJoin"
+#define HINT_NONESTLOOP                        "NoNestLoop"
+#define HINT_NOMERGEJOIN               "NoMergeJoin"
+#define HINT_NOHASHJOIN                        "NoHashJoin"
+#define HINT_LEADING                   "Leading"
+#define HINT_SET                               "Set"
+
 
 #define HINT_ARRAY_DEFAULT_INITSIZE 8
 
@@ -105,29 +105,39 @@ typedef struct SetHint
        char   *value;
 } SetHint;
 
+/*
+ * Describes a context of hint processing.
+ */
 typedef struct PlanHint
 {
-       char       *hint_str;
+       char       *hint_str;           /* original hint string */
 
-       int                     nscan_hints;
-       int                     max_scan_hints;
-       ScanHint  **scan_hints;
+       /* for scan method hints */
+       int                     nscan_hints;    /* # of valid scan hints */
+       int                     max_scan_hints; /* # of slots for scan hints */
+       ScanHint  **scan_hints;         /* parsed scan hints */
 
-       int                     njoin_hints;
-       int                     max_join_hints;
-       JoinHint  **join_hints;
+       /* for join method hints */
+       int                     njoin_hints;    /* # of valid join hints */
+       int                     max_join_hints; /* # of slots for join hints */
+       JoinHint  **join_hints;         /* parsed join hints */
 
-       int                     nlevel;
+       int                     nlevel;                 /* # of relations to be joined */
        List      **join_hint_level;
 
-       List       *leading;
+       /* for Leading hints */
+       List       *leading;            /* relation names specified in Leading hint */
 
-       GucContext      context;
-       List       *set_hints;
+       /* for Set hints */
+       GucContext      context;                /* which GUC parameters can we set? */
+       List       *set_hints;          /* parsed Set hints */
 } PlanHint;
 
 typedef const char *(*HintParserFunction) (PlanHint *plan, Query *parse, char *keyword, const char *str);
 
+/*
+ * Describes a hint parser module which is bound with particular hint keyword.
+ */
 typedef struct HintParser
 {
        char   *keyword;
@@ -1557,6 +1567,10 @@ rebuild_join_hints(PlanHint *plan, PlannerInfo *root, int level, List *initial_r
                        plan->join_hint_level[njoinrels] = lappend(NIL, hint);
                else
                {
+                       /*
+                        * Here relnames is not set, since Relids bitmap is sufficient to
+                        * control paths of this query afterwards.
+                        */
                        hint = JoinHintCreate();
                        hint->nrels = njoinrels;
                        hint->enforce_mask = ENABLE_ALL_JOIN;