Fix concurrent indexing operations with temporary tables

Attempting to use CREATE INDEX, DROP INDEX or REINDEX with CONCURRENTLY
on a temporary relation with ON COMMIT actions triggered unexpected
errors because those operations use multiple transactions internally to
complete their work.  Here is for example one confusing error when using
ON COMMIT DELETE ROWS:
ERROR:  index "foo" already contains data

Issues related to temporary relations and concurrent indexing are fixed
in this commit by enforcing the non-concurrent path to be taken for
temporary relations even if using CONCURRENTLY, transparently to the
user.  Using a non-concurrent path does not matter in practice as locks
cannot be taken on a temporary relation by a session different than the
one owning the relation, and the non-concurrent operation is more
effective.

The problem exists with REINDEX since v12 with the introduction of
CONCURRENTLY, and with CREATE/DROP INDEX since CONCURRENTLY exists for
those commands.  In all supported versions, this caused only confusing
error messages to be generated.  Note that with REINDEX, it was also
possible to issue a REINDEX CONCURRENTLY for a temporary relation owned
by a different session, leading to a server crash.

The idea to enforce transparently the non-concurrent code path for
temporary relations comes originally from Andres Freund.

Reported-by: Manuel Rigger
Author: Michael Paquier, Heikki Linnakangas
Reviewed-by: Andres Freund, Álvaro Herrera, Heikki Linnakangas
Discussion: https://postgr.es/m/CA+u7OA6gP7YAeCguyseusYcc=uR8+ypjCcgDDCTzjQ+k6S9ksQ@mail.gmail.com
Backpatch-through: 9.4

diff --git a/doc/src/sgml/ref/create_index.sgml b/doc/src/sgml/ref/create_index.sgml
index e9f47c441456e065de238d46ab92ba2cfea11db3..da8acfaf9a67e60898b12aa86de9d8d6ff59060e 100644 (file)
--- a/doc/src/sgml/ref/create_index.sgml
+++ b/doc/src/sgml/ref/create_index.sgml
@@ -123,6 +123,11 @@ CREATE [ UNIQUE ] INDEX [ CONCURRENTLY ] [ [ IF NOT EXISTS ] <replaceable class=
         &mdash; see <xref linkend="SQL-CREATEINDEX-CONCURRENTLY"
         endterm="SQL-CREATEINDEX-CONCURRENTLY-title">.
        </para>
+       <para>
+        For temporary tables, <command>CREATE INDEX</command> is always
+        non-concurrent, as no other session can access them, and
+        non-concurrent index creation is cheaper.
+       </para>
       </listitem>
      </varlistentry>
 

diff --git a/doc/src/sgml/ref/drop_index.sgml b/doc/src/sgml/ref/drop_index.sgml
index 6fe108ded25f6e264aaf52fffc1fad9b271d1872..4c0c48ab1ea76ce83c3143c76c81489423c19262 100644 (file)
--- a/doc/src/sgml/ref/drop_index.sgml
+++ b/doc/src/sgml/ref/drop_index.sgml
@@ -58,6 +58,11 @@ DROP INDEX [ CONCURRENTLY ] [ IF EXISTS ] <replaceable class="PARAMETER">name</r
       performed within a transaction block, but
       <command>DROP INDEX CONCURRENTLY</> cannot.
      </para>
+     <para>
+      For temporary tables, <command>DROP INDEX</command> is always
+      non-concurrent, as no other session can access them, and
+      non-concurrent index drop is cheaper.
+     </para>
     </listitem>
    </varlistentry>
 

diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c
index 9386485db230ae3691f4d710148a35a83e85565d..4e901c39a67df783dae4d417ea1ac34856a1dbc2 100644 (file)
--- a/src/backend/catalog/index.c
+++ b/src/backend/catalog/index.c
@@ -1361,6 +1361,15 @@ index_drop(Oid indexId, bool concurrent)
    LOCKTAG     heaplocktag;
    LOCKMODE    lockmode;
 
+   /*
+    * A temporary relation uses a non-concurrent DROP.  Other backends can't
+    * access a temporary relation, so there's no harm in grabbing a stronger
+    * lock (see comments in RemoveRelations), and a non-concurrent DROP is
+    * more efficient.
+    */
+   Assert(get_rel_persistence(indexId) != RELPERSISTENCE_TEMP ||
+          !concurrent);
+
    /*
     * To drop an index safely, we must grab exclusive lock on its parent
     * table.  Exclusive lock on the index alone is insufficient because

diff --git a/src/backend/commands/indexcmds.c b/src/backend/commands/indexcmds.c
index 756d30c2770c282baab136d5ea7bf70bf3b6d139..71a76159cd9afa4a2f6201742e768f1b7d26d7e9 100644 (file)
--- a/src/backend/commands/indexcmds.c
+++ b/src/backend/commands/indexcmds.c
@@ -310,6 +310,7 @@ DefineIndex(Oid relationId,
            bool skip_build,
            bool quiet)
 {
+   bool        concurrent;
    char       *indexRelationName;
    char       *accessMethodName;
    Oid        *typeObjectId;
@@ -340,6 +341,18 @@ DefineIndex(Oid relationId,
    Snapshot    snapshot;
    int         i;
 
+   /*
+    * Force non-concurrent build on temporary relations, even if CONCURRENTLY
+    * was requested.  Other backends can't access a temporary relation, so
+    * there's no harm in grabbing a stronger lock, and a non-concurrent DROP
+    * is more efficient.  Do this before any use of the concurrent option is
+    * done.
+    */
+   if (stmt->concurrent && get_rel_persistence(relationId) != RELPERSISTENCE_TEMP)
+       concurrent = true;
+   else
+       concurrent = false;
+
    /*
     * count attributes in index
     */
@@ -365,7 +378,7 @@ DefineIndex(Oid relationId,
     * relation.  To avoid lock upgrade hazards, that lock should be at least
     * as strong as the one we take here.
     */
-   lockmode = stmt->concurrent ? ShareUpdateExclusiveLock : ShareLock;
+   lockmode = concurrent ? ShareUpdateExclusiveLock : ShareLock;
    rel = heap_open(relationId, lockmode);
 
    relationId = RelationGetRelid(rel);
@@ -557,8 +570,8 @@ DefineIndex(Oid relationId,
    indexInfo->ii_ExclusionStrats = NULL;
    indexInfo->ii_Unique = stmt->unique;
    /* In a concurrent build, mark it not-ready-for-inserts */
-   indexInfo->ii_ReadyForInserts = !stmt->concurrent;
-   indexInfo->ii_Concurrent = stmt->concurrent;
+   indexInfo->ii_ReadyForInserts = !concurrent;
+   indexInfo->ii_Concurrent = concurrent;
    indexInfo->ii_BrokenHotChain = false;
 
    typeObjectId = (Oid *) palloc(numberOfAttributes * sizeof(Oid));
@@ -644,7 +657,7 @@ DefineIndex(Oid relationId,
     * A valid stmt->oldNode implies that we already have a built form of the
     * index.  The caller should also decline any index build.
     */
-   Assert(!OidIsValid(stmt->oldNode) || (skip_build && !stmt->concurrent));
+   Assert(!OidIsValid(stmt->oldNode) || (skip_build && !concurrent));
 
    /*
     * Make the catalog entries for the index, including constraints. Then, if
@@ -658,8 +671,8 @@ DefineIndex(Oid relationId,
                     coloptions, reloptions, stmt->primary,
                     stmt->isconstraint, stmt->deferrable, stmt->initdeferred,
                     allowSystemTableMods,
-                    skip_build || stmt->concurrent,
-                    stmt->concurrent, !check_rights,
+                    skip_build || concurrent,
+                    concurrent, !check_rights,
                     stmt->if_not_exists);
 
    ObjectAddressSet(address, RelationRelationId, indexRelationId);
@@ -675,7 +688,7 @@ DefineIndex(Oid relationId,
        CreateComments(indexRelationId, RelationRelationId, 0,
                       stmt->idxcomment);
 
-   if (!stmt->concurrent)
+   if (!concurrent)
    {
        /* Close the heap and we're done, in the non-concurrent case */
        heap_close(rel, NoLock);

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index d0f2f7c8eb909b76eb0f092003ccc76c79b2139e..9c6ca7ff9c7fe67d66e84646359f3f3dcb32de28 100644 (file)
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -816,7 +816,11 @@ RemoveRelations(DropStmt *drop)
    /* DROP CONCURRENTLY uses a weaker lock, and has some restrictions */
    if (drop->concurrent)
    {
-       flags |= PERFORM_DELETION_CONCURRENTLY;
+       /*
+        * Note that for temporary relations this lock may get upgraded
+        * later on, but as no other session can access a temporary
+        * relation, this is actually fine.
+        */
        lockmode = ShareUpdateExclusiveLock;
        Assert(drop->removeType == OBJECT_INDEX);
        if (list_length(drop->objects) != 1)
@@ -907,6 +911,18 @@ RemoveRelations(DropStmt *drop)
            continue;
        }
 
+       /*
+        * Decide if concurrent mode needs to be used here or not.  The
+        * relation persistence cannot be known without its OID.
+        */
+       if (drop->concurrent &&
+           get_rel_persistence(relOid) != RELPERSISTENCE_TEMP)
+       {
+           Assert(list_length(drop->objects) == 1 &&
+                  drop->removeType == OBJECT_INDEX);
+           flags |= PERFORM_DELETION_CONCURRENTLY;
+       }
+
        /* OK, we're ready to delete this one */
        obj.classId = RelationRelationId;
        obj.objectId = relOid;

diff --git a/src/test/regress/expected/create_index.out b/src/test/regress/expected/create_index.out
index 1db29f81e4688125ddc57fabc9ca2405df01f239..66be26735d7a45d4ae98aeed126638f3eb779aec 100644 (file)
--- a/src/test/regress/expected/create_index.out
+++ b/src/test/regress/expected/create_index.out
@@ -2519,6 +2519,31 @@ Indexes:
     "concur_index5" btree (f2) WHERE f1 = 'x'::text
     "std_index" btree (f2)
 
+-- Temporary tables with concurrent builds and on-commit actions
+-- CONCURRENTLY used with CREATE INDEX and DROP INDEX is ignored.
+-- PRESERVE ROWS, the default.
+CREATE TEMP TABLE concur_temp (f1 int, f2 text)
+  ON COMMIT PRESERVE ROWS;
+INSERT INTO concur_temp VALUES (1, 'foo'), (2, 'bar');
+CREATE INDEX CONCURRENTLY concur_temp_ind ON concur_temp(f1);
+DROP INDEX CONCURRENTLY concur_temp_ind;
+DROP TABLE concur_temp;
+-- ON COMMIT DROP
+BEGIN;
+CREATE TEMP TABLE concur_temp (f1 int, f2 text)
+  ON COMMIT DROP;
+INSERT INTO concur_temp VALUES (1, 'foo'), (2, 'bar');
+-- Fails when running in a transaction.
+CREATE INDEX CONCURRENTLY concur_temp_ind ON concur_temp(f1);
+ERROR:  CREATE INDEX CONCURRENTLY cannot run inside a transaction block
+COMMIT;
+-- ON COMMIT DELETE ROWS
+CREATE TEMP TABLE concur_temp (f1 int, f2 text)
+  ON COMMIT DELETE ROWS;
+INSERT INTO concur_temp VALUES (1, 'foo'), (2, 'bar');
+CREATE INDEX CONCURRENTLY concur_temp_ind ON concur_temp(f1);
+DROP INDEX CONCURRENTLY concur_temp_ind;
+DROP TABLE concur_temp;
 --
 -- Try some concurrent index drops
 --

diff --git a/src/test/regress/sql/create_index.sql b/src/test/regress/sql/create_index.sql
index 74bb36659656722a214765a302986bc402add90a..73763327aca4c04127dbf3eb9a8dadbc973a3288 100644 (file)
--- a/src/test/regress/sql/create_index.sql
+++ b/src/test/regress/sql/create_index.sql
@@ -795,6 +795,31 @@ VACUUM FULL concur_heap;
 REINDEX TABLE concur_heap;
 \d concur_heap
 
+-- Temporary tables with concurrent builds and on-commit actions
+-- CONCURRENTLY used with CREATE INDEX and DROP INDEX is ignored.
+-- PRESERVE ROWS, the default.
+CREATE TEMP TABLE concur_temp (f1 int, f2 text)
+  ON COMMIT PRESERVE ROWS;
+INSERT INTO concur_temp VALUES (1, 'foo'), (2, 'bar');
+CREATE INDEX CONCURRENTLY concur_temp_ind ON concur_temp(f1);
+DROP INDEX CONCURRENTLY concur_temp_ind;
+DROP TABLE concur_temp;
+-- ON COMMIT DROP
+BEGIN;
+CREATE TEMP TABLE concur_temp (f1 int, f2 text)
+  ON COMMIT DROP;
+INSERT INTO concur_temp VALUES (1, 'foo'), (2, 'bar');
+-- Fails when running in a transaction.
+CREATE INDEX CONCURRENTLY concur_temp_ind ON concur_temp(f1);
+COMMIT;
+-- ON COMMIT DELETE ROWS
+CREATE TEMP TABLE concur_temp (f1 int, f2 text)
+  ON COMMIT DELETE ROWS;
+INSERT INTO concur_temp VALUES (1, 'foo'), (2, 'bar');
+CREATE INDEX CONCURRENTLY concur_temp_ind ON concur_temp(f1);
+DROP INDEX CONCURRENTLY concur_temp_ind;
+DROP TABLE concur_temp;
+
 --
 -- Try some concurrent index drops
 --