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Add support for partial TOAST decompression

When asked for a slice of a TOAST entry, decompress enough to return the
slice instead of decompressing the entire object.

For use cases where the slice is at, or near, the beginning of the entry,
this avoids a lot of unnecessary decompression work.

This changes the signature of pglz_decompress() by adding a boolean to
indicate if it's ok for the call to finish before consuming all of the
source or destination buffers.

Author: Paul Ramsey
Reviewed-By: Rafia Sabih, Darafei Praliaskouski, Regina Obe
Discussion: https://postgr.es/m/CACowWR07EDm7Y4m2kbhN_jnys%3DBBf9A6768RyQdKm_%3DNpkcaWg%40mail.gmail.com
This commit is contained in:
Stephen Frost
2019-04-02 12:35:32 -04:00
parent d50d172e51
commit 4d0e994eed
5 changed files with 70 additions and 36 deletions

View File

@ -1425,7 +1425,7 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
{
/* If a backup block image is compressed, decompress it */
if (pglz_decompress(ptr, bkpb->bimg_len, tmp.data,
BLCKSZ - bkpb->hole_length) < 0)
BLCKSZ - bkpb->hole_length, true) < 0)
{
report_invalid_record(record, "invalid compressed image at %X/%X, block %d",
(uint32) (record->ReadRecPtr >> 32),