Add SysCacheGetAttrNotNull for guaranteed not-null attrs

When extracting an attr from a cached tuple in the syscache with
SysCacheGetAttr the isnull parameter must be checked in case the
attr cannot be NULL.  For cases when this is known beforehand, a
wrapper is introduced which perform the errorhandling internally
on behalf of the caller, invoking an elog in case of a NULL attr.

Reviewed-by: Tom Lane <[email protected]>
Reviewed-by: Peter Eisentraut <[email protected]>
Reviewed-by: David Rowley <[email protected]>
Discussion: https://postgr.es/m/[email protected]

3 files changed, 36 insertions, 22 deletions

diff --git a/src/backend/utils/cache/lsyscache.c b/src/backend/utils/cache/lsyscache.c
index c07382051d6..c7607895cdd 100644
--- a/src/backend/utils/cache/lsyscache.c
+++ b/src/backend/utils/cache/lsyscache.c
@@ -3195,7 +3195,6 @@ get_attstatsslot(AttStatsSlot *sslot, HeapTuple statstuple,
 	Form_pg_statistic stats = (Form_pg_statistic) GETSTRUCT(statstuple);
 	int			i;
 	Datum		val;
-	bool		isnull;
 	ArrayType  *statarray;
 	Oid			arrayelemtype;
 	int			narrayelem;
@@ -3219,11 +3218,8 @@ get_attstatsslot(AttStatsSlot *sslot, HeapTuple statstuple,
 
 	if (flags & ATTSTATSSLOT_VALUES)
 	{
-		val = SysCacheGetAttr(STATRELATTINH, statstuple,
-							  Anum_pg_statistic_stavalues1 + i,
-							  &isnull);
-		if (isnull)
-			elog(ERROR, "stavalues is null");
+		val = SysCacheGetAttrNotNull(STATRELATTINH, statstuple,
+									 Anum_pg_statistic_stavalues1 + i);
 
 		/*
 		 * Detoast the array if needed, and in any case make a copy that's
@@ -3267,11 +3263,8 @@ get_attstatsslot(AttStatsSlot *sslot, HeapTuple statstuple,
 
 	if (flags & ATTSTATSSLOT_NUMBERS)
 	{
-		val = SysCacheGetAttr(STATRELATTINH, statstuple,
-							  Anum_pg_statistic_stanumbers1 + i,
-							  &isnull);
-		if (isnull)
-			elog(ERROR, "stanumbers is null");
+		val = SysCacheGetAttrNotNull(STATRELATTINH, statstuple,
+									 Anum_pg_statistic_stanumbers1 + i);
 
 		/*
 		 * Detoast the array if needed, and in any case make a copy that's
@@ -3479,7 +3472,6 @@ get_index_column_opclass(Oid index_oid, int attno)
 	HeapTuple	tuple;
 	Form_pg_index rd_index;
 	Datum		datum;
-	bool		isnull;
 	oidvector  *indclass;
 	Oid			opclass;
 
@@ -3501,10 +3493,7 @@ get_index_column_opclass(Oid index_oid, int attno)
 		return InvalidOid;
 	}
 
-	datum = SysCacheGetAttr(INDEXRELID, tuple,
-							Anum_pg_index_indclass, &isnull);
-	Assert(!isnull);
-
+	datum = SysCacheGetAttrNotNull(INDEXRELID, tuple, Anum_pg_index_indclass);
 	indclass = ((oidvector *) DatumGetPointer(datum));
 
 	Assert(attno <= indclass->dim1);
diff --git a/src/backend/utils/cache/partcache.c b/src/backend/utils/cache/partcache.c
index 4f53d472333..5f3516ad0c2 100644
--- a/src/backend/utils/cache/partcache.c
+++ b/src/backend/utils/cache/partcache.c
@@ -130,15 +130,13 @@ RelationBuildPartitionKey(Relation relation)
 
 	/* But use the hard way to retrieve further variable-length attributes */
 	/* Operator class */
-	datum = SysCacheGetAttr(PARTRELID, tuple,
-							Anum_pg_partitioned_table_partclass, &isnull);
-	Assert(!isnull);
+	datum = SysCacheGetAttrNotNull(PARTRELID, tuple,
+								   Anum_pg_partitioned_table_partclass);
 	opclass = (oidvector *) DatumGetPointer(datum);
 
 	/* Collation */
-	datum = SysCacheGetAttr(PARTRELID, tuple,
-							Anum_pg_partitioned_table_partcollation, &isnull);
-	Assert(!isnull);
+	datum = SysCacheGetAttrNotNull(PARTRELID, tuple,
+								   Anum_pg_partitioned_table_partcollation);
 	collation = (oidvector *) DatumGetPointer(datum);
 
 	/* Expressions */
diff --git a/src/backend/utils/cache/syscache.c b/src/backend/utils/cache/syscache.c
index 94abede512b..4e4a34bde80 100644
--- a/src/backend/utils/cache/syscache.c
+++ b/src/backend/utils/cache/syscache.c
@@ -77,6 +77,7 @@
 #include "catalog/pg_user_mapping.h"
 #include "lib/qunique.h"
 #include "utils/catcache.h"
+#include "utils/lsyscache.h"
 #include "utils/rel.h"
 #include "utils/syscache.h"
 
@@ -1100,6 +1101,32 @@ SysCacheGetAttr(int cacheId, HeapTuple tup,
 }
 
 /*
+ * SysCacheGetAttrNotNull
+ *
+ * As above, a version of SysCacheGetAttr which knows that the attr cannot
+ * be NULL.
+ */
+Datum
+SysCacheGetAttrNotNull(int cacheId, HeapTuple tup,
+					   AttrNumber attributeNumber)
+{
+	bool		isnull;
+	Datum		attr;
+
+	attr = SysCacheGetAttr(cacheId, tup, attributeNumber, &isnull);
+
+	if (isnull)
+	{
+		elog(ERROR,
+			 "unexpected null value in cached tuple for catalog %s column %s",
+			 get_rel_name(cacheinfo[cacheId].reloid),
+			 NameStr(TupleDescAttr(SysCache[cacheId]->cc_tupdesc, attributeNumber - 1)->attname));
+	}
+
+	return attr;
+}
+
+/*
  * GetSysCacheHashValue
  *
  * Get the hash value that would be used for a tuple in the specified cache