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Clean up some minor inefficiencies in parallel dump/restore.

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Parallel dump did a totally pointless query to find out the name of each
table to be dumped, which it already knows.  Parallel restore runs issued
lots of redundant SET commands because _doSetFixedOutputState() was invoked
once per TOC item rather than just once at connection start.  While the
extra queries are insignificant if you're dumping or restoring large
tables, it still seems worth getting rid of them.

Also, give the responsibility for selecting the right client_encoding for
a parallel dump worker to setup_connection() where it naturally belongs,
instead of having ad-hoc code for that in CloneArchive().  And fix some
minor bugs like use of strdup() where pg_strdup() would be safer.

Back-patch to 9.3, mostly to keep the branches in sync in an area that
we're still finding bugs in.

Discussion: <5086.1464793073@sss.pgh.pa.us>
This commit is contained in:
Tom Lane
2016-06-01 16:14:21 -04:00
parent 47215c16f2
commit 43d3fbe369
3 changed files with 34 additions and 50 deletions
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26
src/bin/pg_dump/parallel.c
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@@ -801,7 +801,6 @@ IsEveryWorkerIdle(ParallelState *pstate)
static void
lockTableForWorker(ArchiveHandle *AH, TocEntry *te)
{
Archive *AHX = (Archive *) AH;
const char *qualId;
PQExpBuffer query;
PGresult *res;
@@ -812,33 +811,10 @@ lockTableForWorker(ArchiveHandle *AH, TocEntry *te)
query = createPQExpBuffer();
/*
* XXX this is an unbelievably expensive substitute for knowing how to dig
* a table name out of a TocEntry.
*/
appendPQExpBuffer(query,
"SELECT pg_namespace.nspname,"
" pg_class.relname "
" FROM pg_class "
" JOIN pg_namespace on pg_namespace.oid = relnamespace "
" WHERE pg_class.oid = %u", te->catalogId.oid);
res = PQexec(AH->connection, query->data);
if (!res || PQresultStatus(res) != PGRES_TUPLES_OK)
exit_horribly(modulename,
"could not get relation name for OID %u: %s\n",
te->catalogId.oid, PQerrorMessage(AH->connection));
resetPQExpBuffer(query);
qualId = fmtQualifiedId(AHX->remoteVersion,
PQgetvalue(res, 0, 0),
PQgetvalue(res, 0, 1));
qualId = fmtQualifiedId(AH->public.remoteVersion, te->namespace, te->tag);
appendPQExpBuffer(query, "LOCK TABLE %s IN ACCESS SHARE MODE NOWAIT",
qualId);
PQclear(res);
res = PQexec(AH->connection, query->data);