database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-07-28 23:42:10 +03:00
Code Activity

Refactor XLogReadRecord(), adding XLogBeginRead() function.

Browse Source 
The signature of XLogReadRecord() required the caller to pass the starting
WAL position as argument, or InvalidXLogRecPtr to continue reading at the
end of previous record. That's slightly awkward to the callers, as most
of them don't want to randomly jump around in the WAL stream, but start
reading at one position and then read everything from that point onwards.
Remove the 'RecPtr' argument and add a new function XLogBeginRead() to
specify the starting position instead. That's more convenient for the
callers. Also, xlogreader holds state that is reset when you change the
starting position, so having a separate function for doing that feels like
a more natural fit.

This changes XLogFindNextRecord() function so that it doesn't reset the
xlogreader's state to what it was before the call anymore. Instead, it
positions the xlogreader to the found record, like XLogBeginRead().

Reviewed-by: Kyotaro Horiguchi, Alvaro Herrera
Discussion: https://www.postgresql.org/message-id/5382a7a3-debe-be31-c860-cb810c08f366%40iki.fi
This commit is contained in:
Heikki Linnakangas
2020-01-26 11:39:00 +02:00
parent 1001368497
commit 38a957316d
10 changed files with 102 additions and 97 deletions
Download Patch File Download Diff File Expand all files Collapse all files

7
src/backend/replication/logical/logical.c
View File

@ -461,11 +461,10 @@ DecodingContextReady(LogicalDecodingContext *ctx)
void
DecodingContextFindStartpoint(LogicalDecodingContext *ctx)
{
XLogRecPtr startptr;
ReplicationSlot *slot = ctx->slot;
/* Initialize from where to start reading WAL. */
startptr = slot->data.restart_lsn;
XLogBeginRead(ctx->reader, slot->data.restart_lsn);
elog(DEBUG1, "searching for logical decoding starting point, starting at %X/%X",
(uint32) (slot->data.restart_lsn >> 32),
@ -478,14 +477,12 @@ DecodingContextFindStartpoint(LogicalDecodingContext *ctx)
char *err = NULL;
/* the read_page callback waits for new WAL */
record = XLogReadRecord(ctx->reader, startptr, &err);
record = XLogReadRecord(ctx->reader, &err);
if (err)
elog(ERROR, "%s", err);
if (!record)
elog(ERROR, "no record found"); /* shouldn't happen */
startptr = InvalidXLogRecPtr;
LogicalDecodingProcessRecord(ctx, ctx->reader);
/* only continue till we found a consistent spot */