farrokhi/pg_repack
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

Add comment explaining how race condition between CREATE TABLE ... AS SELECT and recording of log entries is avoided.

Browse Source
This commit is contained in:
Josh Kupershmidt 2012-11-29 20:27:33 -07:00
parent d402a73e42
commit 3b856623fd
1 changed files with 10 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
bin/pg_repack.c
View File

@ -507,6 +507,10 @@ repack_one_table(const repack_table *table, const char *orderby)
*/
elog(DEBUG2, "---- copy tuples ----");
/* Must use SERIALIZABLE (or at least not READ COMMITTED) to avoid race
* condition between the create_table statement and rows subsequently
* being added to the log.
*/
command("BEGIN ISOLATION LEVEL SERIALIZABLE", 0, NULL);
/* SET work_mem = maintenance_work_mem */
command("SELECT set_config('work_mem', current_setting('maintenance_work_mem'), true)", 0, NULL);
@ -515,6 +519,12 @@ repack_one_table(const repack_table *table, const char *orderby)
res = execute(SQL_XID_SNAPSHOT, 0, NULL);
vxid = strdup(PQgetvalue(res, 0, 0));
PQclear(res);
/* Delete any existing entries in the log table now, since we have not
* yet run the CREATE TABLE ... AS SELECT, which will take in all existing
* rows from the target table; if we also included prior rows from the
* log we could wind up with duplicates.
*/
command(table->delete_log, 0, NULL);
command(table->create_table, 0, NULL);
printfStringInfo(&sql, "SELECT repack.disable_autovacuum('repack.table_%u')", table->target_oid);