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Add support for prepared transactions to built-in logical replication.

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To add support for streaming transactions at prepare time into the
built-in logical replication, we need to do the following things:

* Modify the output plugin (pgoutput) to implement the new two-phase API
callbacks, by leveraging the extended replication protocol.

* Modify the replication apply worker, to properly handle two-phase
transactions by replaying them on prepare.

* Add a new SUBSCRIPTION option "two_phase" to allow users to enable
two-phase transactions. We enable the two_phase once the initial data sync
is over.

We however must explicitly disable replication of two-phase transactions
during replication slot creation, even if the plugin supports it. We
don't need to replicate the changes accumulated during this phase,
and moreover, we don't have a replication connection open so we don't know
where to send the data anyway.

The streaming option is not allowed with this new two_phase option. This
can be done as a separate patch.

We don't allow to toggle two_phase option of a subscription because it can
lead to an inconsistent replica. For the same reason, we don't allow to
refresh the publication once the two_phase is enabled for a subscription
unless copy_data option is false.

Author: Peter Smith, Ajin Cherian and Amit Kapila based on previous work by Nikhil Sontakke and Stas Kelvich
Reviewed-by: Amit Kapila, Sawada Masahiko, Vignesh C, Dilip Kumar, Takamichi Osumi, Greg Nancarrow
Tested-By: Haiying Tang
Discussion: https://postgr.es/m/02DA5F5E-CECE-4D9C-8B4B-418077E2C010@postgrespro.ru
Discussion: https://postgr.es/m/CAA4eK1+opiV4aFTmWWUF9h_32=HfPOW9vZASHarT0UA5oBrtGw@mail.gmail.com
This commit is contained in:
Amit Kapila
2021-07-14 07:33:50 +05:30
parent 6c9c283166
commit a8fd13cab0
43 changed files with 2382 additions and 191 deletions
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25
src/backend/replication/logical/reorderbuffer.c
View File

@ -2576,7 +2576,7 @@ ReorderBufferReplay(ReorderBufferTXN *txn,
txn->final_lsn = commit_lsn;
txn->end_lsn = end_lsn;
txn->commit_time = commit_time;
txn->xact_time.commit_time = commit_time;
txn->origin_id = origin_id;
txn->origin_lsn = origin_lsn;
@ -2667,7 +2667,7 @@ ReorderBufferRememberPrepareInfo(ReorderBuffer *rb, TransactionId xid,
*/
txn->final_lsn = prepare_lsn;
txn->end_lsn = end_lsn;
txn->commit_time = prepare_time;
txn->xact_time.prepare_time = prepare_time;
txn->origin_id = origin_id;
txn->origin_lsn = origin_lsn;
@ -2714,7 +2714,7 @@ ReorderBufferPrepare(ReorderBuffer *rb, TransactionId xid,
Assert(txn->final_lsn != InvalidXLogRecPtr);
ReorderBufferReplay(txn, rb, xid, txn->final_lsn, txn->end_lsn,
txn->commit_time, txn->origin_id, txn->origin_lsn);
txn->xact_time.prepare_time, txn->origin_id, txn->origin_lsn);
/*
* We send the prepare for the concurrently aborted xacts so that later
@ -2734,7 +2734,7 @@ ReorderBufferPrepare(ReorderBuffer *rb, TransactionId xid,
void
ReorderBufferFinishPrepared(ReorderBuffer *rb, TransactionId xid,
XLogRecPtr commit_lsn, XLogRecPtr end_lsn,
XLogRecPtr initial_consistent_point,
XLogRecPtr two_phase_at,
TimestampTz commit_time, RepOriginId origin_id,
XLogRecPtr origin_lsn, char *gid, bool is_commit)
{
@ -2753,19 +2753,20 @@ ReorderBufferFinishPrepared(ReorderBuffer *rb, TransactionId xid,
* be later used for rollback.
*/
prepare_end_lsn = txn->end_lsn;
prepare_time = txn->commit_time;
prepare_time = txn->xact_time.prepare_time;
/* add the gid in the txn */
txn->gid = pstrdup(gid);
/*
* It is possible that this transaction is not decoded at prepare time
* either because by that time we didn't have a consistent snapshot or it
* was decoded earlier but we have restarted. We only need to send the
* prepare if it was not decoded earlier. We don't need to decode the xact
* for aborts if it is not done already.
* either because by that time we didn't have a consistent snapshot, or
* two_phase was not enabled, or it was decoded earlier but we have
* restarted. We only need to send the prepare if it was not decoded
* earlier. We don't need to decode the xact for aborts if it is not done
* already.
*/
if ((txn->final_lsn < initial_consistent_point) && is_commit)
if ((txn->final_lsn < two_phase_at) && is_commit)
{
txn->txn_flags |= RBTXN_PREPARE;
@ -2783,12 +2784,12 @@ ReorderBufferFinishPrepared(ReorderBuffer *rb, TransactionId xid,
* prepared after the restart.
*/
ReorderBufferReplay(txn, rb, xid, txn->final_lsn, txn->end_lsn,
txn->commit_time, txn->origin_id, txn->origin_lsn);
txn->xact_time.prepare_time, txn->origin_id, txn->origin_lsn);
}
txn->final_lsn = commit_lsn;
txn->end_lsn = end_lsn;
txn->commit_time = commit_time;
txn->xact_time.commit_time = commit_time;
txn->origin_id = origin_id;
txn->origin_lsn = origin_lsn;