Prevent reindex of invalid indexes on TOAST tables

Such indexes can only be duplicated leftovers of a previously failed
REINDEX CONCURRENTLY command, and a valid equivalent is guaranteed to
exist.  As toast indexes can only be dropped if invalid, reindexing
these would lead to useless duplicated indexes that can't be dropped
anymore, except if the parent relation is dropped.

Thanks to Justin Pryzby for reminding that this problem was reported
long ago during the review of the original patch of REINDEX
CONCURRENTLY, but the issue was never addressed.

Reported-by: Sergei Kornilov, Justin Pryzby
Author: Julien Rouhaud
Reviewed-by: Michael Paquier
Discussion: https://postgr.es/m/36712441546604286%40sas1-890ba5c2334a.qloud-c.yandex.net
Discussion: https://postgr.es/m/20200216190835.GA21832@telsasoft.com
Backpatch-through: 12

diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c
index 72236790338fc20bd86a8255e67bc6b8699b5805..76fd938ce33047b0e70c1bcd43423f8df518c779 100644 (file)
--- a/src/backend/catalog/index.c
+++ b/src/backend/catalog/index.c
@@ -3474,6 +3474,17 @@ reindex_index(Oid indexId, bool skip_constraint_checks, char persistence,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("cannot reindex temporary tables of other sessions")));
 
+   /*
+    * Don't allow reindex of an invalid index on TOAST table.  This is a
+    * leftover from a failed REINDEX CONCURRENTLY, and if rebuilt it would
+    * not be possible to drop it anymore.
+    */
+   if (IsToastNamespace(RelationGetNamespace(iRel)) &&
+       !get_index_isvalid(indexId))
+       ereport(ERROR,
+               (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+                errmsg("cannot reindex invalid index on TOAST table")));
+
    /*
     * Also check for active uses of the index in the current transaction; we
     * don't want to reindex underneath an open indexscan.
@@ -3723,6 +3734,23 @@ reindex_relation(Oid relid, int flags, int options)
        foreach(indexId, indexIds)
        {
            Oid         indexOid = lfirst_oid(indexId);
+           Oid         indexNamespaceId = get_rel_namespace(indexOid);
+
+           /*
+            * Skip any invalid indexes on a TOAST table.  These can only be
+            * duplicate leftovers from a failed REINDEX CONCURRENTLY, and if
+            * rebuilt it would not be possible to drop them anymore.
+            */
+           if (IsToastNamespace(indexNamespaceId) &&
+               !get_index_isvalid(indexOid))
+           {
+               ereport(WARNING,
+                       (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+                        errmsg("cannot reindex invalid index \"%s.%s\" on TOAST table, skipping",
+                               get_namespace_name(indexNamespaceId),
+                               get_rel_name(indexOid))));
+               continue;
+           }
 
            reindex_index(indexOid, !(flags & REINDEX_REL_CHECK_CONSTRAINTS),
                          persistence, options);

diff --git a/src/backend/commands/indexcmds.c b/src/backend/commands/indexcmds.c
index 3f3a89fe922835608814693696f09e9a39baf227..6d696dd672bf864340716396a04a44f7a5992334 100644 (file)
--- a/src/backend/commands/indexcmds.c
+++ b/src/backend/commands/indexcmds.c
@@ -2868,6 +2868,16 @@ ReindexRelationConcurrently(Oid relationOid, int options)
                            (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                             errmsg("cannot reindex system catalogs concurrently")));
 
+               /*
+                * Don't allow reindex for an invalid index on TOAST table, as
+                * if rebuild it would not be possible to drop it.
+                */
+               if (IsToastNamespace(get_rel_namespace(relationOid)) &&
+                   !get_index_isvalid(relationOid))
+                   ereport(ERROR,
+                           (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+                            errmsg("cannot reindex invalid index on TOAST table concurrently")));
+
                /* Save the list of relation OIDs in private context */
                oldcontext = MemoryContextSwitchTo(private_context);
 

diff --git a/src/backend/utils/cache/lsyscache.c b/src/backend/utils/cache/lsyscache.c
index 3da90cb72aea9a92fe810361f6117b133965c2e0..400e7689fe27916cc6ac4715746b1443644b1ed9 100644 (file)
--- a/src/backend/utils/cache/lsyscache.c
+++ b/src/backend/utils/cache/lsyscache.c
@@ -3227,3 +3227,26 @@ get_index_column_opclass(Oid index_oid, int attno)
 
    return opclass;
 }
+
+/*
+ * get_index_isvalid
+ *
+ *     Given the index OID, return pg_index.indisvalid.
+ */
+bool
+get_index_isvalid(Oid index_oid)
+{
+   bool        isvalid;
+   HeapTuple   tuple;
+   Form_pg_index rd_index;
+
+   tuple = SearchSysCache1(INDEXRELID, ObjectIdGetDatum(index_oid));
+   if (!HeapTupleIsValid(tuple))
+       elog(ERROR, "cache lookup failed for index %u", index_oid);
+
+   rd_index = (Form_pg_index) GETSTRUCT(tuple);
+   isvalid = rd_index->indisvalid;
+   ReleaseSysCache(tuple);
+
+   return isvalid;
+}

diff --git a/src/include/utils/lsyscache.h b/src/include/utils/lsyscache.h
index f132d3945817bbc46bd050a7ad0b3744ab777769..131d10eab07698b499eb18f972ef15b97791979f 100644 (file)
--- a/src/include/utils/lsyscache.h
+++ b/src/include/utils/lsyscache.h
@@ -181,6 +181,7 @@ extern char *get_namespace_name_or_temp(Oid nspid);
 extern Oid get_range_subtype(Oid rangeOid);
 extern Oid get_range_collation(Oid rangeOid);
 extern Oid get_index_column_opclass(Oid index_oid, int attno);
+extern bool get_index_isvalid(Oid index_oid);
 
 #define type_is_array(typid)  (get_element_type(typid) != InvalidOid)
 /* type_is_array_domain accepts both plain arrays and domains over arrays */