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Commitcc609c4

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Allow pg_dump to use jobs and serializable transactions together.
Since 9.3, when the --jobs option was introduced, using it togetherwith the --serializable-deferrable option generated multipleerrors. We can get correct behavior by allowing the connectionwhich acquires the snapshot to use SERIALIZABLE, READ ONLY,DEFERRABLE and pass that to the workers running the otherconnections using REPEATABLE READ, READ ONLY. This is a bit of akluge since the SERIALIZABLE behavior is achieved by running someof the participating connections at a different isolation level,but it is a simple and safe change, suitable for back-patching.This will be followed by a proposal for a more invasive fix withsome slight behavioral changes on just the master branch, based onsuggestions from Andres Freund, but the kluge will be applied tomaster until something is agreed along those lines.Back-patched to 9.3, where the --jobs option was added.Based on report from Alexander Korotkov
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‎src/bin/pg_dump/pg_dump.c

Lines changed: 9 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1004,7 +1004,15 @@ setup_connection(Archive *AH, const char *dumpencoding, char *use_role)
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ExecuteSqlStatement(AH,"BEGIN");
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if (AH->remoteVersion >=90100)
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{
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if (serializable_deferrable)
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/*
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* To support the combination of serializable_deferrable with the jobs
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* option we use REPEATABLE READ for the worker connections that are
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* passed a snapshot. As long as the snapshot is acquired in a
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* SERIALIZABLE, READ ONLY, DEFERRABLE transaction, its use within a
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* REPEATABLE READ transaction provides the appropriate integrity
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* guarantees. This is a kluge, but safe for back-patching.
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*/
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if (serializable_deferrable&&AH->sync_snapshot_id==NULL)
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ExecuteSqlStatement(AH,
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"SET TRANSACTION ISOLATION LEVEL "
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"SERIALIZABLE, READ ONLY, DEFERRABLE");

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