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Generic Messages for Logical Decoding

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API and mechanism to allow generic messages to be inserted into WAL that are
intended to be read by logical decoding plugins. This commit adds an optional
new callback to the logical decoding API.

Messages are either text or bytea. Messages can be transactional, or not, and
are identified by a prefix to allow multiple concurrent decoding plugins.

(Not to be confused with Generic WAL records, which are intended to allow crash
recovery of extensible objects.)

Author: Petr Jelinek and Andres Freund
Reviewers: Artur Zakirov, Tomas Vondra, Simon Riggs
Discussion: 5685F999.6010202@2ndquadrant.com
This commit is contained in:
Simon Riggs
2016-04-06 10:05:41 +01:00
parent 989be0810d
commit 3fe3511d05
27 changed files with 693 additions and 33 deletions
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19
src/backend/replication/logical/snapbuild.c
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@@ -604,6 +604,25 @@ SnapBuildExportSnapshot(SnapBuild *builder)
return snapname;
}
/*
* Ensure there is a snapshot and if not build one for current transaction.
*/
Snapshot
SnapBuildGetOrBuildSnapshot(SnapBuild *builder, TransactionId xid)
{
Assert(builder->state == SNAPBUILD_CONSISTENT);
/* only build a new snapshot if we don't have a prebuilt one */
if (builder->snapshot == NULL)
{
builder->snapshot = SnapBuildBuildSnapshot(builder, xid);
/* inrease refcount for the snapshot builder */
SnapBuildSnapIncRefcount(builder->snapshot);
}
return builder->snapshot;
}
/*
* Reset a previously SnapBuildExportSnapshot()'ed snapshot if there is
* any. Aborts the previously started transaction and resets the resource