Diagnose !indisvalid in more SQL functions.

pgstatindex failed with ERRCODE_DATA_CORRUPTED, of the "can't-happen"
class XX.  The other functions succeeded on an empty index; they might
have malfunctioned if the failed index build left torn I/O or other
complex state.  Report an ERROR in statistics functions pgstatindex,
pgstatginindex, pgstathashindex, and pgstattuple.  Report DEBUG1 and
skip all index I/O in maintenance functions brin_desummarize_range,
brin_summarize_new_values, brin_summarize_range, and
gin_clean_pending_list.  Back-patch to v11 (all supported versions).

Discussion: https://postgr.es/m/20231001195309.a3@google.com

contrib/pgstattuple/pgstatindex.c

@@ -237,6 +237,18 @@ pgstatindex_impl(Relation rel, FunctionCallInfo fcinfo)
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 				 errmsg("cannot access temporary tables of other sessions")));
 
+	/*
+	 * A !indisready index could lead to ERRCODE_DATA_CORRUPTED later, so exit
+	 * early.  We're capable of assessing an indisready&&!indisvalid index,
+	 * but the results could be confusing.  For example, the index's size
+	 * could be too low for a valid index of the table.
+	 */
+	if (!rel->rd_index->indisvalid)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("index \"%s\" is not valid",
+						RelationGetRelationName(rel))));
+
 	/*
 	 * Read metapage
 	 */
@@ -523,6 +535,13 @@ pgstatginindex_internal(Oid relid, FunctionCallInfo fcinfo)
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 				 errmsg("cannot access temporary indexes of other sessions")));
 
+	/* see pgstatindex_impl */
+	if (!rel->rd_index->indisvalid)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("index \"%s\" is not valid",
+						RelationGetRelationName(rel))));
+
 	/*
 	 * Read metapage
 	 */
@@ -600,6 +619,13 @@ pgstathashindex(PG_FUNCTION_ARGS)
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 				 errmsg("cannot access temporary indexes of other sessions")));
 
+	/* see pgstatindex_impl */
+	if (!rel->rd_index->indisvalid)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("index \"%s\" is not valid",
+						RelationGetRelationName(rel))));
+
 	/* Get the information we need from the metapage. */
 	memset(&stats, 0, sizeof(stats));
 	metabuf = _hash_getbuf(rel, HASH_METAPAGE, HASH_READ, LH_META_PAGE);

contrib/pgstattuple/pgstattuple.c

@@ -259,6 +259,13 @@ pgstat_relation(Relation rel, FunctionCallInfo fcinfo)
 	}
 	else if (rel->rd_rel->relkind == RELKIND_INDEX)
 	{
+		/* see pgstatindex_impl */
+		if (!rel->rd_index->indisvalid)
+			ereport(ERROR,
+					(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+					 errmsg("index \"%s\" is not valid",
+							RelationGetRelationName(rel))));
+
 		switch (rel->rd_rel->relam)
 		{
 			case BTREE_AM_OID:

src/backend/access/brin/brin.c

@@ -1100,8 +1100,14 @@ brin_summarize_range(PG_FUNCTION_ARGS)
 				 errmsg("could not open parent table of index \"%s\"",
 						RelationGetRelationName(indexRel))));
 
-	/* OK, do it */
+	/* see gin_clean_pending_list() */
-	brinsummarize(indexRel, heapRel, heapBlk, true, &numSummarized, NULL);
+	if (indexRel->rd_index->indisvalid)
+		brinsummarize(indexRel, heapRel, heapBlk, true, &numSummarized, NULL);
+	else
+		ereport(DEBUG1,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("index \"%s\" is not valid",
+						RelationGetRelationName(indexRel))));
 
 	/* Roll back any GUC changes executed by index functions */
 	AtEOXact_GUC(false, save_nestlevel);
@@ -1183,12 +1189,21 @@ brin_desummarize_range(PG_FUNCTION_ARGS)
 				 errmsg("could not open parent table of index \"%s\"",
 						RelationGetRelationName(indexRel))));
 
-	/* the revmap does the hard work */
+	/* see gin_clean_pending_list() */
-	do
+	if (indexRel->rd_index->indisvalid)
 	{
-		done = brinRevmapDesummarizeRange(indexRel, heapBlk);
+		/* the revmap does the hard work */
+		do
+		{
+			done = brinRevmapDesummarizeRange(indexRel, heapBlk);
+		}
+		while (!done);
 	}
-	while (!done);
+	else
+		ereport(DEBUG1,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("index \"%s\" is not valid",
+						RelationGetRelationName(indexRel))));
 
 	relation_close(indexRel, ShareUpdateExclusiveLock);
 	relation_close(heapRel, ShareUpdateExclusiveLock);

src/backend/access/gin/ginfast.c

@@ -1033,7 +1033,6 @@ gin_clean_pending_list(PG_FUNCTION_ARGS)
 	Oid			indexoid = PG_GETARG_OID(0);
 	Relation	indexRel = index_open(indexoid, RowExclusiveLock);
 	IndexBulkDeleteResult stats;
-	GinState	ginstate;
 
 	if (RecoveryInProgress())
 		ereport(ERROR,
@@ -1065,8 +1064,26 @@ gin_clean_pending_list(PG_FUNCTION_ARGS)
 					   RelationGetRelationName(indexRel));
 
 	memset(&stats, 0, sizeof(stats));
-	initGinState(&ginstate, indexRel);
+
-	ginInsertCleanup(&ginstate, true, true, true, &stats);
+	/*
+	 * Can't assume anything about the content of an !indisready index.  Make
+	 * those a no-op, not an error, so users can just run this function on all
+	 * indexes of the access method.  Since an indisready&&!indisvalid index
+	 * is merely awaiting missed aminsert calls, we're capable of processing
+	 * it.  Decline to do so, out of an abundance of caution.
+	 */
+	if (indexRel->rd_index->indisvalid)
+	{
+		GinState	ginstate;
+
+		initGinState(&ginstate, indexRel);
+		ginInsertCleanup(&ginstate, true, true, true, &stats);
+	}
+	else
+		ereport(DEBUG1,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("index \"%s\" is not valid",
+						RelationGetRelationName(indexRel))));
 
 	index_close(indexRel, RowExclusiveLock);