On Mon, Feb 23, 2015 at 5:28 PM, Rahila Syed <rahilasyed90@gmail.com> wrote: > Hello, > > Attached is a patch which has following changes, > > As suggested above block ID in xlog structs has been replaced by chunk ID. > Chunk ID is used to distinguish between different types of xlog record > fragments. > Like, > XLR_CHUNK_ID_DATA_SHORT > XLR_CHUNK_ID_DATA_LONG > XLR_CHUNK_BKP_COMPRESSED > XLR_CHUNK_BKP_WITH_HOLE > > In block references, block ID follows the chunk ID. Here block ID retains > its functionality. > This approach increases data by 1 byte for each block reference in an xlog > record. This approach separates ID referring different fragments of xlog > record from the actual block ID which is used to refer block references in > xlog record.
I've not read this logic yet, but ISTM there is a bug in that new WAL format because I got the following error and the startup process could not replay any WAL records when I set up replication and enabled wal_compression.
LOG: record with invalid length at 0/30000B0 LOG: record with invalid length at 0/3000518 LOG: Invalid block length in record 0/30005A0 LOG: Invalid block length in record 0/3000D60
Looking at this code, I think that it is really confusing to move the data related to the status of the backup block out of XLogRecordBlockImageHeader to the chunk ID itself that may *not* include a backup block at all as it is conditioned by the presence of BKPBLOCK_HAS_IMAGE. I would still prefer the idea of having the backup block data in its dedicated header with bits stolen from the existing fields, perhaps by rewriting it to something like that:
Wouldn't we need a XLR_CHUNK_ID_BKP_HEADER or equivalent? The idea between this chunk_id stuff it to be able to make the difference between a short header, a long header and a backup block header by looking at the first byte.
The comments on top of XLogRecordBlockImageHeader are still mentioning the old parameters like with_hole or is_compressed that you have removed.
It seems as well that there is some noise: - lp_off and lp_len fields in ItemIdData (see include/storage/itemid.h). + lp_off and lp_len fields in ItemIdData (see include/storage/itemid.h)
From:
Michael Paquier Date: Subject:
Re: Enforce creation of destination folders for source
files in pg_regress (Was: pg_regress writes into source tree)
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