diff options
| author | Tom Lane | 2019-05-22 15:46:57 +0000 |
|---|---|---|
| committer | Tom Lane | 2019-05-22 15:47:02 +0000 |
| commit | 166f69f769c83ef8759d905bf7f1a9aa1d97a340 (patch) | |
| tree | e4e7dcc6de3e1bac0007126c42451fb1e0cef169 | |
| parent | 728840fe13acff7b03a4b1a813eeb8900ce5e469 (diff) | |
Fix O(N^2) performance issue in pg_publication_tables view.
The original coding of this view relied on a correlated IN sub-query.
Our planner is not very bright about correlated sub-queries, and even
if it were, there's no way for it to know that the output of
pg_get_publication_tables() is duplicate-free, making the de-duplicating
semantics of IN unnecessary. Hence, rewrite as a LATERAL sub-query.
This provides circa 100X speedup for me with a few hundred published
tables (the whole regression database), and things would degrade as
roughly O(published_relations * all_relations) beyond that.
Because the rules.out expected output changes, force a catversion bump.
Ordinarily we might not want to do that post-beta1; but we already know
we'll be doing a catversion bump before beta2 to fix pg_statistic_ext
issues, so it's pretty much free to fix it now instead of waiting for v13.
Per report and fix suggestion from PegoraroF10.
Discussion: https://postgr.es/m/1551385426763-0.post@n3.nabble.com
| -rw-r--r-- | src/backend/catalog/system_views.sql | 7 | ||||
| -rw-r--r-- | src/include/catalog/catversion.h | 2 | ||||
| -rw-r--r-- | src/test/regress/expected/rules.out | 4 |
3 files changed, 7 insertions, 6 deletions
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql index 566100d6df2..52a6c315840 100644 --- a/src/backend/catalog/system_views.sql +++ b/src/backend/catalog/system_views.sql @@ -258,9 +258,10 @@ CREATE VIEW pg_publication_tables AS P.pubname AS pubname, N.nspname AS schemaname, C.relname AS tablename - FROM pg_publication P, pg_class C - JOIN pg_namespace N ON (N.oid = C.relnamespace) - WHERE C.oid IN (SELECT relid FROM pg_get_publication_tables(P.pubname)); + FROM pg_publication P, + LATERAL pg_get_publication_tables(P.pubname) GPT, + pg_class C JOIN pg_namespace N ON (N.oid = C.relnamespace) + WHERE C.oid = GPT.relid; CREATE VIEW pg_locks AS SELECT * FROM pg_lock_status() AS L; diff --git a/src/include/catalog/catversion.h b/src/include/catalog/catversion.h index c5c06163aa3..474d48c8ee3 100644 --- a/src/include/catalog/catversion.h +++ b/src/include/catalog/catversion.h @@ -53,6 +53,6 @@ */ /* yyyymmddN */ -#define CATALOG_VERSION_NO 201905141 +#define CATALOG_VERSION_NO 201905221 #endif diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out index 0c392e51e21..4363ca16633 100644 --- a/src/test/regress/expected/rules.out +++ b/src/test/regress/expected/rules.out @@ -1441,10 +1441,10 @@ pg_publication_tables| SELECT p.pubname, n.nspname AS schemaname, c.relname AS tablename FROM pg_publication p, + LATERAL pg_get_publication_tables((p.pubname)::text) gpt(relid), (pg_class c JOIN pg_namespace n ON ((n.oid = c.relnamespace))) - WHERE (c.oid IN ( SELECT pg_get_publication_tables.relid - FROM pg_get_publication_tables((p.pubname)::text) pg_get_publication_tables(relid))); + WHERE (c.oid = gpt.relid); pg_replication_origin_status| SELECT pg_show_replication_origin_status.local_id, pg_show_replication_origin_status.external_id, pg_show_replication_origin_status.remote_lsn, |