pg_walsummary - Man Page

• Convert a WAL summary file to text: pg_walsummary path/to/file
• Print one line per individual modified block (rather than ranges): pg_walsummary [-i|--individual] path/to/file
• Suppress normal output (only errors): pg_walsummary [-q|--quiet] path/to/file

tldr.sh

pg_walsummary [option...] [file...]

pg_walsummary is used to print the contents of WAL summary files​. These binary files are found with the pg_wal/summaries subdirectory of the data directory, and can be converted to text using this tool​. This is not ordinarily necessary, since WAL summary files primarily exist to support incremental backup, but it may be useful for debugging purposes​.

A WAL summary file is indexed by tablespace OID, relation OID, and relation fork​. For each relation fork, it stores the list of blocks that were modified by WAL within the range summarized in the file​. It can also store a "limit block," which is 0 if the relation fork was created or truncated within the relevant WAL range, and otherwise the shortest length to which the relation fork was truncated​. If the relation fork was not created, deleted, or truncated within the relevant WAL range, the limit block is undefined or infinite and will not be printed by this tool​.

-i

--individual

By default, pg_walsummary prints one line of output for each range of one or more consecutive modified blocks​. This can make the output a lot briefer, since a relation where all blocks from 0 through 999 were modified will produce only one line of output rather than 1000 separate lines​. This option requests a separate line of output for every modified block​.

-q

--quiet

Do not print any output, except for errors​. This can be useful when you want to know whether a WAL summary file can be successfully parsed but don't care about the contents​.

-V

--version

Display version information, then exit​.

-?

--help

Shows help about pg_walsummary command line arguments, and exits​.

The environment variable PG_COLOR specifies whether to use color in diagnostic messages​. Possible values are always, auto and never​.

pg_basebackup(1), pg_combinebackup(1)