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Allow altering of two_phase option of a SUBSCRIPTION.

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The two_phase option is controlled by both the publisher (as a slot
option) and the subscriber (as a subscription option), so the slot option
must also be modified.

Changing the 'two_phase' option for a subscription from 'true' to 'false'
is permitted only when there are no pending prepared transactions
corresponding to that subscription. Otherwise, the changes of already
prepared transactions can be replicated again along with their corresponding
commit leading to duplicate data or errors.

To avoid data loss, the 'two_phase' option for a subscription can only be
changed from 'false' to 'true' once the initial data synchronization is
completed. Therefore this is performed later by the logical replication worker.

Author: Hayato Kuroda, Ajin Cherian, Amit Kapila
Reviewed-by: Peter Smith, Hou Zhijie, Amit Kapila, Vitaly Davydov, Vignesh C
Discussion: https://postgr.es/m/8fab8-65d74c80-1-2f28e880@39088166
This commit is contained in:
Amit Kapila
2024-07-24 10:13:36 +05:30
parent 774d47b6c0
commit 1462aad2e4
17 changed files with 458 additions and 120 deletions
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79
src/backend/access/transam/twophase.c
View File

@@ -2681,3 +2681,82 @@ LookupGXact(const char *gid, XLogRecPtr prepare_end_lsn,
LWLockRelease(TwoPhaseStateLock);
return found;
}
/*
* TwoPhaseTransactionGid
* Form the prepared transaction GID for two_phase transactions.
*
* Return the GID in the supplied buffer.
*/
void
TwoPhaseTransactionGid(Oid subid, TransactionId xid, char *gid_res, int szgid)
{
Assert(OidIsValid(subid));
if (!TransactionIdIsValid(xid))
ereport(ERROR,
(errcode(ERRCODE_PROTOCOL_VIOLATION),
errmsg_internal("invalid two-phase transaction ID")));
snprintf(gid_res, szgid, "pg_gid_%u_%u", subid, xid);
}
/*
* IsTwoPhaseTransactionGidForSubid
* Check whether the given GID (as formed by TwoPhaseTransactionGid) is
* for the specified 'subid'.
*/
static bool
IsTwoPhaseTransactionGidForSubid(Oid subid, char *gid)
{
int ret;
Oid subid_from_gid;
TransactionId xid_from_gid;
char gid_tmp[GIDSIZE];
/* Extract the subid and xid from the given GID */
ret = sscanf(gid, "pg_gid_%u_%u", &subid_from_gid, &xid_from_gid);
/*
* Check that the given GID has expected format, and at least the subid
* matches.
*/
if (ret != 2 || subid != subid_from_gid)
return false;
/*
* Reconstruct a temporary GID based on the subid and xid extracted from
* the given GID and check whether the temporary GID and the given GID
* match.
*/
TwoPhaseTransactionGid(subid, xid_from_gid, gid_tmp, sizeof(gid_tmp));
return strcmp(gid, gid_tmp) == 0;
}
/*
* LookupGXactBySubid
* Check if the prepared transaction done by apply worker exists.
*/
bool
LookupGXactBySubid(Oid subid)
{
bool found = false;
LWLockAcquire(TwoPhaseStateLock, LW_SHARED);
for (int i = 0; i < TwoPhaseState->numPrepXacts; i++)
{
GlobalTransaction gxact = TwoPhaseState->prepXacts[i];
/* Ignore not-yet-valid GIDs. */
if (gxact->valid &&
IsTwoPhaseTransactionGidForSubid(subid, gxact->gid))
{
found = true;
break;
}
}
LWLockRelease(TwoPhaseStateLock);
return found;
}