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Disallow CREATE INDEX if table is already in use in current session.

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If we allow this, whatever outer command has the table open will not know
about the new index and may fail to update it as needed, as shown in a
report from Laurenz Albe.  We already had such a prohibition in place for
ALTER TABLE, but the CREATE INDEX syntax missed the check.

Fixing it requires an API change for DefineIndex(), which conceivably
would break third-party extensions if we were to back-patch it.  Given
how long this problem has existed without being noticed, fixing it in
the back branches doesn't seem worth that risk.

Discussion: https://postgr.es/m/A737B7A37273E048B164557ADEF4A58B53A4DC9A@ntex2010i.host.magwien.gv.at
This commit is contained in:
Tom Lane
2017-06-04 12:02:31 -04:00
parent 55a70a023c
commit 0d18852666
7 changed files with 78 additions and 0 deletions
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13
src/backend/commands/indexcmds.c
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@ -295,6 +295,9 @@ CheckIndexCompatible(Oid oldId,
* 'is_alter_table': this is due to an ALTER rather than a CREATE operation.
* 'check_rights': check for CREATE rights in namespace and tablespace. (This
* should be true except when ALTER is deleting/recreating an index.)
* 'check_not_in_use': check for table not already in use in current session.
* This should be true unless caller is holding the table open, in which
* case the caller had better have checked it earlier.
* 'skip_build': make the catalog entries but leave the index file empty;
* it will be filled later.
* 'quiet': suppress the NOTICE chatter ordinarily provided for constraints.
@ -307,6 +310,7 @@ DefineIndex(Oid relationId,
Oid indexRelationId,
bool is_alter_table,
bool check_rights,
bool check_not_in_use,
bool skip_build,
bool quiet)
{
@ -404,6 +408,15 @@ DefineIndex(Oid relationId,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot create indexes on temporary tables of other sessions")));
/*
* Unless our caller vouches for having checked this already, insist that
* the table not be in use by our own session, either. Otherwise we might
* fail to make entries in the new index (for instance, if an INSERT or
* UPDATE is in progress and has already made its list of target indexes).
*/
if (check_not_in_use)
CheckTableNotInUse(rel, "CREATE INDEX");
/*
* Verify we (still) have CREATE rights in the rel's namespace.
* (Presumably we did when the rel was created, but maybe not anymore.)