farrokhi/pg_repack
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Use our own namespace for advisory locks.

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Switch to using the two-input form of pg_advisory_lock(), so as
to avoid impacting other applications which might happen to lock
just the OID of the table. The REPACK_LOCK_PREFIX_STR is a decimal
version of the first three bytes of
  echo -n "pg_repack" | sha1sum
This commit is contained in:
Josh Kupershmidt 2013-06-22 09:56:44 -04:00
parent bebe6ffb2b
commit 61bf8acaf0
1 changed files with 16 additions and 15 deletions
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31
bin/pg_repack.c
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@ -126,6 +126,9 @@ const char *PROGRAM_VERSION = "unknown";
" AND granted = false AND relation = %u"\ " AND granted = false AND relation = %u"\
" AND mode = 'AccessExclusiveLock' AND pid <> pg_backend_pid()" " AND mode = 'AccessExclusiveLock' AND pid <> pg_backend_pid()"
/* Will be used as a unique prefix for advisory locks. */
#define REPACK_LOCK_PREFIX_STR "16185446"
/* /*
* per-table information * per-table information
*/ */
@ -1300,8 +1303,10 @@ repack_one_table(const repack_table *table, const char *orderby)
} }
/* Release advisory lock on table. */ /* Release advisory lock on table. */
res = pgut_execute(connection, "SELECT pg_advisory_unlock($1::bigint)", params[0] = REPACK_LOCK_PREFIX_STR;
1, params); params[1] = buffer;
res = pgut_execute(connection, "SELECT pg_advisory_unlock($1, $2)",
2, params);
ret = true; ret = true;
cleanup: cleanup:
@ -1452,14 +1457,6 @@ lock_access_share(PGconn *conn, Oid relid, const char *target_name)
} }
/* XXX: Make sure that repack_one_table() also obtains an advisory
* lock on the table, so that we can't have a table-wide repack running
* along with an indexes-only repack. Also, since advisory locks are
* 8 bytes wide and OIDs are only 4 bytes, consider using our own prefix
* rather than just the table OID, to avoid inadvertent conflict with
* other applications using advisory locks.
*/
/* Obtain an advisory lock on the table's OID, to make sure no other /* Obtain an advisory lock on the table's OID, to make sure no other
* pg_repack is working on the table. This is not so much a concern with * pg_repack is working on the table. This is not so much a concern with
* full-table repacks, but mainly so that index-only repacks don't interfere * full-table repacks, but mainly so that index-only repacks don't interfere
@ -1467,11 +1464,15 @@ lock_access_share(PGconn *conn, Oid relid, const char *target_name)
*/ */
static bool advisory_lock(PGconn *conn, const char *relid) static bool advisory_lock(PGconn *conn, const char *relid)
{ {
PGresult *res = NULL; PGresult *res = NULL;
bool ret = false; bool ret = false;
const char *params[2];
res = pgut_execute(conn, "SELECT pg_try_advisory_lock($1::bigint)", params[0] = REPACK_LOCK_PREFIX_STR;
1, &relid); params[1] = relid;
res = pgut_execute(conn, "SELECT pg_try_advisory_lock($1, $2)",
2, params);
if (PQresultStatus(res) != PGRES_TUPLES_OK) { if (PQresultStatus(res) != PGRES_TUPLES_OK) {
elog(ERROR, "%s", PQerrorMessage(connection)); elog(ERROR, "%s", PQerrorMessage(connection));
@ -1790,7 +1791,7 @@ repack_all_indexes(char *errbuf, size_t errsize)
* table. * table.
*/ */
if (!advisory_lock(connection, utoa(getoid(res, 0, 3), buffer))) { if (!advisory_lock(connection, utoa(getoid(res, 0, 3), buffer))) {
snprintf(errbuf, errsize, "Unable to obtain advisory lock on %s", snprintf(errbuf, errsize, "Unable to obtain advisory lock on \"%s\"",
table_name); table_name);
goto cleanup; goto cleanup;
} }