v3-0006-Create-create_stat_ext_entry-from-fetch_statentri.patch

From 0797a698495c21baaef3b633e78425bcd7b16821 Mon Sep 17 00:00:00 2001
From: Corey Huinker <corey.huinker@gmail.com>
Date: Mon, 11 Dec 2023 03:23:28 -0500
Subject: [PATCH v3 6/9] Create create_stat_ext_entry() from
 fetch_statentries_for_relation().

Refactor fetch_statentries_for_relation() to use create_stat_ext_entry() in
its inner loop.

Later commits will make use of create_stat_ext_entry().

This was made its own commit for code clarity.
---
 src/backend/statistics/extended_stats.c | 146 +++++++++++++-----------
 1 file changed, 78 insertions(+), 68 deletions(-)

diff --git a/src/backend/statistics/extended_stats.c b/src/backend/statistics/extended_stats.c
index 7f014a0cbb..718826ecf1 100644
--- a/src/backend/statistics/extended_stats.c
+++ b/src/backend/statistics/extended_stats.c
@@ -418,6 +418,83 @@ statext_is_kind_built(HeapTuple htup, char type)
 	return !heap_attisnull(htup, attnum, NULL);
 }
 
+/*
+ * Create a single StatExtEntry from a fetched heap tuple
+ */
+static StatExtEntry *
+create_stat_ext_entry(HeapTuple htup)
+{
+	StatExtEntry *entry;
+	Datum		datum;
+	bool		isnull;
+	int			i;
+	ArrayType  *arr;
+	char	   *enabled;
+	Form_pg_statistic_ext staForm;
+	List	   *exprs = NIL;
+
+	entry = palloc0(sizeof(StatExtEntry));
+	staForm = (Form_pg_statistic_ext) GETSTRUCT(htup);
+	entry->statOid = staForm->oid;
+	entry->schema = get_namespace_name(staForm->stxnamespace);
+	entry->name = pstrdup(NameStr(staForm->stxname));
+	entry->stattarget = staForm->stxstattarget;
+	for (i = 0; i < staForm->stxkeys.dim1; i++)
+	{
+		entry->columns = bms_add_member(entry->columns,
+										staForm->stxkeys.values[i]);
+	}
+
+	/* decode the stxkind char array into a list of chars */
+	datum = SysCacheGetAttrNotNull(STATEXTOID, htup,
+								   Anum_pg_statistic_ext_stxkind);
+	arr = DatumGetArrayTypeP(datum);
+	if (ARR_NDIM(arr) != 1 ||
+		ARR_HASNULL(arr) ||
+		ARR_ELEMTYPE(arr) != CHAROID)
+		elog(ERROR, "stxkind is not a 1-D char array");
+	enabled = (char *) ARR_DATA_PTR(arr);
+	for (i = 0; i < ARR_DIMS(arr)[0]; i++)
+	{
+		Assert((enabled[i] == STATS_EXT_NDISTINCT) ||
+			   (enabled[i] == STATS_EXT_DEPENDENCIES) ||
+			   (enabled[i] == STATS_EXT_MCV) ||
+			   (enabled[i] == STATS_EXT_EXPRESSIONS));
+		entry->types = lappend_int(entry->types, (int) enabled[i]);
+	}
+
+	/* decode expression (if any) */
+	datum = SysCacheGetAttr(STATEXTOID, htup,
+							Anum_pg_statistic_ext_stxexprs, &isnull);
+
+	if (!isnull)
+	{
+		char	   *exprsString;
+
+		exprsString = TextDatumGetCString(datum);
+		exprs = (List *) stringToNode(exprsString);
+
+		pfree(exprsString);
+
+		/*
+		 * Run the expressions through eval_const_expressions. This is not
+		 * just an optimization, but is necessary, because the planner
+		 * will be comparing them to similarly-processed qual clauses, and
+		 * may fail to detect valid matches without this.  We must not use
+		 * canonicalize_qual, however, since these aren't qual
+		 * expressions.
+		 */
+		exprs = (List *) eval_const_expressions(NULL, (Node *) exprs);
+
+		/* May as well fix opfuncids too */
+		fix_opfuncids((Node *) exprs);
+	}
+
+	entry->exprs = exprs;
+
+	return entry;
+}
+
 /*
  * Return a list (of StatExtEntry) of statistics objects for the given relation.
  */
@@ -443,74 +520,7 @@ fetch_statentries_for_relation(Relation pg_statext, Oid relid)
 
 	while (HeapTupleIsValid(htup = systable_getnext(scan)))
 	{
-		StatExtEntry *entry;
-		Datum		datum;
-		bool		isnull;
-		int			i;
-		ArrayType  *arr;
-		char	   *enabled;
-		Form_pg_statistic_ext staForm;
-		List	   *exprs = NIL;
-
-		entry = palloc0(sizeof(StatExtEntry));
-		staForm = (Form_pg_statistic_ext) GETSTRUCT(htup);
-		entry->statOid = staForm->oid;
-		entry->schema = get_namespace_name(staForm->stxnamespace);
-		entry->name = pstrdup(NameStr(staForm->stxname));
-		entry->stattarget = staForm->stxstattarget;
-		for (i = 0; i < staForm->stxkeys.dim1; i++)
-		{
-			entry->columns = bms_add_member(entry->columns,
-											staForm->stxkeys.values[i]);
-		}
-
-		/* decode the stxkind char array into a list of chars */
-		datum = SysCacheGetAttrNotNull(STATEXTOID, htup,
-									   Anum_pg_statistic_ext_stxkind);
-		arr = DatumGetArrayTypeP(datum);
-		if (ARR_NDIM(arr) != 1 ||
-			ARR_HASNULL(arr) ||
-			ARR_ELEMTYPE(arr) != CHAROID)
-			elog(ERROR, "stxkind is not a 1-D char array");
-		enabled = (char *) ARR_DATA_PTR(arr);
-		for (i = 0; i < ARR_DIMS(arr)[0]; i++)
-		{
-			Assert((enabled[i] == STATS_EXT_NDISTINCT) ||
-				   (enabled[i] == STATS_EXT_DEPENDENCIES) ||
-				   (enabled[i] == STATS_EXT_MCV) ||
-				   (enabled[i] == STATS_EXT_EXPRESSIONS));
-			entry->types = lappend_int(entry->types, (int) enabled[i]);
-		}
-
-		/* decode expression (if any) */
-		datum = SysCacheGetAttr(STATEXTOID, htup,
-								Anum_pg_statistic_ext_stxexprs, &isnull);
-
-		if (!isnull)
-		{
-			char	   *exprsString;
-
-			exprsString = TextDatumGetCString(datum);
-			exprs = (List *) stringToNode(exprsString);
-
-			pfree(exprsString);
-
-			/*
-			 * Run the expressions through eval_const_expressions. This is not
-			 * just an optimization, but is necessary, because the planner
-			 * will be comparing them to similarly-processed qual clauses, and
-			 * may fail to detect valid matches without this.  We must not use
-			 * canonicalize_qual, however, since these aren't qual
-			 * expressions.
-			 */
-			exprs = (List *) eval_const_expressions(NULL, (Node *) exprs);
-
-			/* May as well fix opfuncids too */
-			fix_opfuncids((Node *) exprs);
-		}
-
-		entry->exprs = exprs;
-
+		StatExtEntry *entry = create_stat_ext_entry(htup);
 		result = lappend(result, entry);
 	}
 
-- 
2.43.0