* ptrack_version() — returns ptrack version string.

* ptrack_init_lsn() — returns LSN of the last ptrack map initialization.

* ptrack_get_pagemapset('LSN') — returns a set of changed data files with bitmaps of changed blocks since specified LSN.

* ptrack_get_pagemapset(start_lsn pg_lsn) — returns a set of changed data files with bitmaps of changed blocks since specified`start_lsn`.

* ptrack_get_change_stat(start_lsn pg_lsn) — returns statistic of changes (number of files, pages and size in MB) since specified`start_lsn`.

* ptrack_get_change_file_stat(start_lsn pg_lsn) — returns per file statistic of changes (number of pages and size in MB) since specified`start_lsn`.

Usage example:

* Do`ALTER EXTENSION 'ptrack' UPDATE;`.

* Restart your server.

Since version 2.2 we use a different algorithm for tracking changed pages. Thus, data recorded in the`ptrack.map` using pre 2.2 versions of`ptrack` is incompatible with newer versions. After extension upgrade and server restart old`ptrack.map` will be discarded with`WARNING` and initialized from the scratch.

1. You can only use`ptrack` safely with`wal_level >= 'replica'`. Otherwise, you can lose tracking of some changes if crash-recovery occurs, since[certain commands are designed not to write WAL at all if wal_level is minimal](https://www.postgresql.org/docs/12/populate.html#POPULATE-PITR), but we only durably flush`ptrack` map at checkpoint time.

FROM ptrack_get_pagemapset(start_lsn)) s;

END

$func$ LANGUAGE plpgsql;

CREATEFUNCTIONptrack_get_change_file_stat(start_lsn pg_lsn)

RETURNS TABLE (

file_pathtext,

pagesint,

)AS

$func$

DECLARE

block_sizebigint;

block_size := (SELECT settingFROM pg_settingsWHERE name='block_size');

RETURN QUERY

SELECTs.path,

changed_pages,

block_size*changed_pages/(1024.0*1024)

(SELECTpath,

length(replace(right((pagemap)::text,-1)::varbit::text,'0',''))

AS changed_pages

FROM ptrack_get_pagemapset(start_lsn)) s

ORDER BY (changed_pages,s.path)DESC;

END

$func$ LANGUAGE plpgsql;

use TestLib;

use Test::More;

plantests=>24;

plantests=>25;

my$node;

my$res;

$res_stdout =$node->safe_psql("postgres","SELECT pages FROM ptrack_get_change_stat('$flush_lsn')");

is($res_stdout > 0, 1,'should be able to get aggregated stats of changes');

$res_stdout =$node->safe_psql("postgres","SELECT count(*) FROM ptrack_get_change_file_stat('$flush_lsn')");

is($res_stdout > 0, 1,'should be able to get per file stats of changes');

$node->append_conf(

'postgresql.conf',q{