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Code Activity

Logical replication support for initial data copy

Browse Source 
Add functionality for a new subscription to copy the initial data in the
tables and then sync with the ongoing apply process.

For the copying, add a new internal COPY option to have the COPY source
data provided by a callback function.  The initial data copy works on
the subscriber by receiving COPY data from the publisher and then
providing it locally into a COPY that writes to the destination table.

A WAL receiver can now execute full SQL commands.  This is used here to
obtain information about tables and publications.

Several new options were added to CREATE and ALTER SUBSCRIPTION to
control whether and when initial table syncing happens.

Change pg_dump option --no-create-subscription-slots to
--no-subscription-connect and use the new CREATE SUBSCRIPTION
... NOCONNECT option for that.

Author: Petr Jelinek <petr.jelinek@2ndquadrant.com>
Tested-by: Erik Rijkers <er@xs4all.nl>
This commit is contained in:
Peter Eisentraut
2017-03-23 08:36:36 -04:00
parent 707576b571
commit 7c4f52409a
62 changed files with 2969 additions and 344 deletions
Download Patch File Download Diff File Expand all files Collapse all files

85
src/backend/replication/logical/snapbuild.c
View File

@ -499,51 +499,32 @@ SnapBuildBuildSnapshot(SnapBuild *builder, TransactionId xid)
}
/*
* Export a snapshot so it can be set in another session with SET TRANSACTION
* SNAPSHOT.
* Build the initial slot snapshot and convert it to normal snapshot that
* is understood by HeapTupleSatisfiesMVCC.
*
* For that we need to start a transaction in the current backend as the
* importing side checks whether the source transaction is still open to make
* sure the xmin horizon hasn't advanced since then.
*
* After that we convert a locally built snapshot into the normal variant
* understood by HeapTupleSatisfiesMVCC et al.
* The snapshot will be usable directly in current transaction or exported
* for loading in different transaction.
*/
const char *
SnapBuildExportSnapshot(SnapBuild *builder)
Snapshot
SnapBuildInitalSnapshot(SnapBuild *builder)
{
Snapshot snap;
char *snapname;
TransactionId xid;
TransactionId *newxip;
int newxcnt = 0;
Assert(!FirstSnapshotSet);
Assert(XactIsoLevel = XACT_REPEATABLE_READ);
if (builder->state != SNAPBUILD_CONSISTENT)
elog(ERROR, "cannot export a snapshot before reaching a consistent state");
elog(ERROR, "cannot build an initial slot snapshot before reaching a consistent state");
if (!builder->committed.includes_all_transactions)
elog(ERROR, "cannot export a snapshot, not all transactions are monitored anymore");
elog(ERROR, "cannot build an initial slot snapshot, not all transactions are monitored anymore");
/* so we don't overwrite the existing value */
if (TransactionIdIsValid(MyPgXact->xmin))
elog(ERROR, "cannot export a snapshot when MyPgXact->xmin already is valid");
if (IsTransactionOrTransactionBlock())
elog(ERROR, "cannot export a snapshot from within a transaction");
if (SavedResourceOwnerDuringExport)
elog(ERROR, "can only export one snapshot at a time");
SavedResourceOwnerDuringExport = CurrentResourceOwner;
ExportInProgress = true;
StartTransactionCommand();
Assert(!FirstSnapshotSet);
/* There doesn't seem to a nice API to set these */
XactIsoLevel = XACT_REPEATABLE_READ;
XactReadOnly = true;
elog(ERROR, "cannot build an initial slot snapshot when MyPgXact->xmin already is valid");
snap = SnapBuildBuildSnapshot(builder, GetTopTransactionId());
@ -578,7 +559,9 @@ SnapBuildExportSnapshot(SnapBuild *builder)
if (test == NULL)
{
if (newxcnt >= GetMaxSnapshotXidCount())
elog(ERROR, "snapshot too large");
ereport(ERROR,
(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
errmsg("initial slot snapshot too large")));
newxip[newxcnt++] = xid;
}
@ -589,9 +572,43 @@ SnapBuildExportSnapshot(SnapBuild *builder)
snap->xcnt = newxcnt;
snap->xip = newxip;
return snap;
}
/*
* Export a snapshot so it can be set in another session with SET TRANSACTION
* SNAPSHOT.
*
* For that we need to start a transaction in the current backend as the
* importing side checks whether the source transaction is still open to make
* sure the xmin horizon hasn't advanced since then.
*/
const char *
SnapBuildExportSnapshot(SnapBuild *builder)
{
Snapshot snap;
char *snapname;
if (IsTransactionOrTransactionBlock())
elog(ERROR, "cannot export a snapshot from within a transaction");
if (SavedResourceOwnerDuringExport)
elog(ERROR, "can only export one snapshot at a time");
SavedResourceOwnerDuringExport = CurrentResourceOwner;
ExportInProgress = true;
StartTransactionCommand();
/* There doesn't seem to a nice API to set these */
XactIsoLevel = XACT_REPEATABLE_READ;
XactReadOnly = true;
snap = SnapBuildInitalSnapshot(builder);
/*
* now that we've built a plain snapshot, use the normal mechanisms for
* exporting it
* now that we've built a plain snapshot, make it active and use the
* normal mechanisms for exporting it
*/
snapname = ExportSnapshot(snap);