Re: logical decoding and replication of sequences, take 2

On Wed, Aug 16, 2023 at 7:57 PM Tomas Vondra
<tomas.vondra@enterprisedb.com> wrote:
>

I was reading through 0001, I noticed this comment in
ReorderBufferSequenceIsTransactional() function

+ * To decide if a sequence change should be handled as transactional or applied
+ * immediately, we track (sequence) relfilenodes created by each transaction.
+ * We don't know if the current sub-transaction was already assigned to the
+ * top-level transaction, so we need to check all transactions.

It says "We don't know if the current sub-transaction was already
assigned to the top-level transaction, so we need to check all
transactions". But IIRC as part of the steaming of in-progress
transactions we have ensured that whenever we are logging the first
change by any subtransaction we include the top transaction ID in it.

Refer this code

LogicalDecodingProcessRecord(LogicalDecodingContext *ctx,
XLogReaderState *record)
{
...
/*
* If the top-level xid is valid, we need to assign the subxact to the
* top-level xact. We need to do this for all records, hence we do it
* before the switch.
*/
if (TransactionIdIsValid(txid))
{
ReorderBufferAssignChild(ctx->reorder,
txid,
XLogRecGetXid(record),
buf.origptr);
}
}

--
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com