digoal
2023-01-04
PostgreSQL , PolarDB , pg_dump , 批量加锁
PostgreSQL 16 preview - pg_dump 批量加表级共享访问锁减少加锁交互时长, 一次query batch length reaches 100K.
+ /*
+ * Tables are locked in batches. When dumping from a remote
+ * server this can save a significant amount of time by reducing
+ * the number of round trips.
+ */
+ if (query->len == 0)
+ appendPQExpBuffer(query, "LOCK TABLE %s",
+ fmtQualifiedDumpable(&tblinfo[i]));
+ else
+ {
+ appendPQExpBuffer(query, ", %s",
+ fmtQualifiedDumpable(&tblinfo[i]));
+
+ /* Arbitrarily end a batch when query length reaches 100K. */
+ if (query->len >= 100000)
+ {
+ /* Lock another batch of tables. */
+ appendPQExpBufferStr(query, " IN ACCESS SHARE MODE");
+ ExecuteSqlStatement(fout, query->data);
+ resetPQExpBuffer(query);
+ }
+ }
During pg_dump startup, acquire table locks in batches.
author Tom Lane <tgl@sss.pgh.pa.us>
Tue, 3 Jan 2023 22:56:37 +0000 (17:56 -0500)
committer Tom Lane <tgl@sss.pgh.pa.us>
Tue, 3 Jan 2023 22:56:44 +0000 (17:56 -0500)
commit 5f53b42cfd053a724fcbe0712a9d5716e576a3e6
tree 34bbc9ea111022775683c7f6ad5e900b1fc6f3bb tree
parent b23837dde48028f9e31983c765c32e3f42cb7ef2 commit | diff
During pg_dump startup, acquire table locks in batches.
Combine multiple LOCK TABLE commands to reduce the number of
round trips to the server. This is particularly helpful when
dumping from a remote server, but it seems useful even without
that. In particular, shortening the time from seeing a table
in pg_class to acquiring lock on it reduces the window for
trouble from concurrent DDL.
Aleksander Alekseev, reviewed by Fabrízio de Royes Mello,
Gilles Darold, and Andres Freund
Discussion: https://postgr.es/m/CAJ7c6TO4z1+OBa-R+fC8FnaUgbEWJUf2Kq=nRngTW5EXtKru2g@mail.gmail.com
