Remove pg_constraint.conincluding

This column was added in commit 8224de4f42cc ("Indexes with INCLUDE
columns and their support in B-tree") to ease writing the ruleutils.c
supporting code for that feature, but it turns out to be unnecessary --
we can do the same thing with just one more syscache lookup.

Even the documentation for the new column being removed in this commit
is awkward.

Discussion: https://postgr.es/m/20180902165018.33otxftp3olgtu4t@alvherre.pgsql

2 files changed, 45 insertions, 33 deletions

diff --git a/src/backend/catalog/pg_constraint.c b/src/backend/catalog/pg_constraint.c
index 7a6d158f898..ea844413608 100644
--- a/src/backend/catalog/pg_constraint.c
+++ b/src/backend/catalog/pg_constraint.c
@@ -85,7 +85,6 @@ CreateConstraintEntry(const char *constraintName,
 	bool		nulls[Natts_pg_constraint];
 	Datum		values[Natts_pg_constraint];
 	ArrayType  *conkeyArray;
-	ArrayType  *conincludingArray;
 	ArrayType  *confkeyArray;
 	ArrayType  *conpfeqopArray;
 	ArrayType  *conppeqopArray;
@@ -116,21 +115,6 @@ CreateConstraintEntry(const char *constraintName,
 	else
 		conkeyArray = NULL;
 
-	if (constraintNTotalKeys > constraintNKeys)
-	{
-		Datum	   *conincluding;
-		int			j = 0;
-		int			constraintNIncludedKeys = constraintNTotalKeys - constraintNKeys;
-
-		conincluding = (Datum *) palloc(constraintNIncludedKeys * sizeof(Datum));
-		for (i = constraintNKeys; i < constraintNTotalKeys; i++)
-			conincluding[j++] = Int16GetDatum(constraintKey[i]);
-		conincludingArray = construct_array(conincluding, constraintNIncludedKeys,
-											INT2OID, 2, true, 's');
-	}
-	else
-		conincludingArray = NULL;
-
 	if (foreignNKeys > 0)
 	{
 		Datum	   *fkdatums;
@@ -204,11 +188,6 @@ CreateConstraintEntry(const char *constraintName,
 	else
 		nulls[Anum_pg_constraint_conkey - 1] = true;
 
-	if (conincludingArray)
-		values[Anum_pg_constraint_conincluding - 1] = PointerGetDatum(conincludingArray);
-	else
-		nulls[Anum_pg_constraint_conincluding - 1] = true;
-
 	if (confkeyArray)
 		values[Anum_pg_constraint_confkey - 1] = PointerGetDatum(confkeyArray);
 	else
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 03e9a28a63b..5cce3f12420 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -315,7 +315,7 @@ static char *deparse_expression_pretty(Node *expr, List *dpcontext,
 static char *pg_get_viewdef_worker(Oid viewoid,
 					  int prettyFlags, int wrapColumn);
 static char *pg_get_triggerdef_worker(Oid trigid, bool pretty);
-static void decompile_column_index_array(Datum column_index_array, Oid relId,
+static int decompile_column_index_array(Datum column_index_array, Oid relId,
 							 StringInfo buf);
 static char *pg_get_ruledef_worker(Oid ruleoid, int prettyFlags);
 static char *pg_get_indexdef_worker(Oid indexrelid, int colno,
@@ -2055,6 +2055,8 @@ pg_get_constraintdef_worker(Oid constraintId, bool fullCommand,
 				Datum		val;
 				bool		isnull;
 				Oid			indexId;
+				int			keyatts;
+				HeapTuple	indtup;
 
 				/* Start off the constraint definition */
 				if (conForm->contype == CONSTRAINT_PRIMARY)
@@ -2069,24 +2071,52 @@ pg_get_constraintdef_worker(Oid constraintId, bool fullCommand,
 					elog(ERROR, "null conkey for constraint %u",
 						 constraintId);
 
-				decompile_column_index_array(val, conForm->conrelid, &buf);
+				keyatts = decompile_column_index_array(val, conForm->conrelid, &buf);
 
 				appendStringInfoChar(&buf, ')');
 
-				/* Fetch and build including column list */
-				isnull = true;
-				val = SysCacheGetAttr(CONSTROID, tup,
-									  Anum_pg_constraint_conincluding, &isnull);
-				if (!isnull)
+				indexId = get_constraint_index(constraintId);
+
+				/* Build including column list (from pg_index.indkeys) */
+				indtup = SearchSysCache1(INDEXRELID, ObjectIdGetDatum(indexId));
+				if (!HeapTupleIsValid(indtup))
+					elog(ERROR, "cache lookup failed for index %u", indexId);
+				val = SysCacheGetAttr(INDEXRELID, indtup,
+									  Anum_pg_index_indnatts, &isnull);
+				if (isnull)
+					elog(ERROR, "null indnatts for index %u", indexId);
+				if (DatumGetInt32(val) > keyatts)
 				{
+					Datum		cols;
+					Datum	   *keys;
+					int			nKeys;
+					int			j;
+
 					appendStringInfoString(&buf, " INCLUDE (");
 
-					decompile_column_index_array(val, conForm->conrelid, &buf);
+					cols = SysCacheGetAttr(INDEXRELID, indtup,
+										   Anum_pg_index_indkey, &isnull);
+					if (isnull)
+						elog(ERROR, "null indkey for index %u", indexId);
+
+					deconstruct_array(DatumGetArrayTypeP(cols),
+									  INT2OID, 2, true, 's',
+									  &keys, NULL, &nKeys);
+
+					for (j = keyatts; j < nKeys; j++)
+					{
+						char	   *colName;
+
+						colName = get_attname(conForm->conrelid,
+											  DatumGetInt16(keys[j]), false);
+						if (j > keyatts)
+							appendStringInfoString(&buf, ", ");
+						appendStringInfoString(&buf, quote_identifier(colName));
+					}
 
 					appendStringInfoChar(&buf, ')');
 				}
-
-				indexId = get_constraint_index(constraintId);
+				ReleaseSysCache(indtup);
 
 				/* XXX why do we only print these bits if fullCommand? */
 				if (fullCommand && OidIsValid(indexId))
@@ -2232,9 +2262,10 @@ pg_get_constraintdef_worker(Oid constraintId, bool fullCommand,
 
 /*
  * Convert an int16[] Datum into a comma-separated list of column names
- * for the indicated relation; append the list to buf.
+ * for the indicated relation; append the list to buf.  Returns the number
+ * of keys.
  */
-static void
+static int
 decompile_column_index_array(Datum column_index_array, Oid relId,
 							 StringInfo buf)
 {
@@ -2258,6 +2289,8 @@ decompile_column_index_array(Datum column_index_array, Oid relId,
 		else
 			appendStringInfo(buf, ", %s", quote_identifier(colName));
 	}
+
+	return nKeys;
 }