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Use pg_current_wal_flush_lsn() starting from 9.6 (#2813)

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Due to historical reasons (not available before 9.6) we used `pg_current_wal_lsn()`/`pg_current_xlog_location()` functions to get current WAL LSN on the primary. But, this LSN is not necessarily synced to disk, and could be lost if the primary node crashed.
This commit is contained in:
Alexander Kukushkin
2023-08-15 09:01:37 +02:00
committed by GitHub
parent 82d2ef4878
commit 6a75b1591b
5 changed files with 21 additions and 8 deletions
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patroni/postgresql/__init__.py
+8 -3
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@@ -57,8 +57,8 @@ class Postgresql(object):
TL_LSN = ("CASE WHEN pg_catalog.pg_is_in_recovery() THEN 0 "
"ELSE ('x' || pg_catalog.substr(pg_catalog.pg_{0}file_name("
"pg_catalog.pg_current_{0}_{1}()), 1, 8))::bit(32)::int END, " # primary timeline
"CASE WHEN pg_catalog.pg_is_in_recovery() THEN 0 "
"ELSE pg_catalog.pg_{0}_{1}_diff(pg_catalog.pg_current_{0}_{1}(), '0/0')::bigint END, " # write_lsn
"CASE WHEN pg_catalog.pg_is_in_recovery() THEN 0 ELSE "
"pg_catalog.pg_{0}_{1}_diff(pg_catalog.pg_current_{0}{2}_{1}(), '0/0')::bigint END, " # wal(_flush)?_lsn
"pg_catalog.pg_{0}_{1}_diff(pg_catalog.pg_last_{0}_replay_{1}(), '0/0')::bigint, "
"pg_catalog.pg_{0}_{1}_diff(COALESCE(pg_catalog.pg_last_{0}_receive_{1}(), '0/0'), '0/0')::bigint, "
"pg_catalog.pg_is_in_recovery() AND pg_catalog.pg_is_{0}_replay_paused()")
@@ -159,6 +159,11 @@ class Postgresql(object):
def wal_name(self) -> str:
return 'wal' if self._major_version >= 100000 else 'xlog'
@property
def wal_flush(self) -> str:
"""For PostgreSQL 9.6 onwards we want to use pg_current_wal_flush_lsn()/pg_current_xlog_flush_location()."""
return '_flush' if self._major_version >= 90600 else ''
@property
def lsn_name(self) -> str:
return 'lsn' if self._major_version >= 100000 else 'location'
@@ -211,7 +216,7 @@ class Postgresql(object):
else:
extra = "0, NULL, NULL, NULL, NULL, NULL, NULL" + extra
return ("SELECT " + self.TL_LSN + ", {2}").format(self.wal_name, self.lsn_name, extra)
return ("SELECT " + self.TL_LSN + ", {3}").format(self.wal_name, self.lsn_name, self.wal_flush, extra)
@property
def available_gucs(self) -> CaseInsensitiveSet: