pg_combinebackup had various problems:
* strncpy was used in various places where strlcpy should be used
instead, to avoid any possibility of the result not being
\0-terminated.
* scan_for_existing_tablespaces() failed to close the directory,
and an error when opening the directory was reported with the
wrong pathname.
* write_reconstructed_file() contained some redundant and therefore
dead code.
* flush_manifest() didn't check the result of pg_checksum_update()
as we do in other places, and misused a local pathname variable
that shouldn't exist at all.
In pg_basebackup, the wrong variable name was used in one place,
due to a copy and paste that was not properly adjusted.
In blkreftable.c, the loop incorrectly doubled chunkno instead of
max_chunks. Fix that. Also remove a nearby assertion per repeated
off-list complaints from Tom Lane.
Per Coverity and subsequent code inspection by me and by Tom Lane.
Discussion: http://postgr.es/m/CA+Tgmobvqqj-DW9F7uUzT-cQqs6wcVb-Xhs=w=hzJnXSE-kRGw@mail.gmail.com
When active, this process writes WAL summary files to
$PGDATA/pg_wal/summaries. Each summary file contains information for a
certain range of LSNs on a certain TLI. For each relation, it stores a
"limit block" which is 0 if a relation is created or destroyed within
a certain range of WAL records, or otherwise the shortest length to
which the relation was truncated during that range of WAL records, or
otherwise InvalidBlockNumber. In addition, it stores a list of blocks
which have been modified during that range of WAL records, but
excluding blocks which were removed by truncation after they were
modified and never subsequently modified again.
In other words, it tells us which blocks need to copied in case of an
incremental backup covering that range of WAL records. But this
doesn't yet add the capability to actually perform an incremental
backup; the next patch will do that.
A new parameter summarize_wal enables or disables this new background
process. The background process also automatically deletes summary
files that are older than wal_summarize_keep_time, if that parameter
has a non-zero value and the summarizer is configured to run.
Patch by me, with some design help from Dilip Kumar and Andres Freund.
Reviewed by Matthias van de Meent, Dilip Kumar, Jakub Wartak, Peter
Eisentraut, and Álvaro Herrera.
Discussion: http://postgr.es/m/CA+TgmoYOYZfMCyOXFyC-P+-mdrZqm5pP2N7S-r0z3_402h9rsA@mail.gmail.com
Robert Haas
Bruce Momjian
Tom Lane