This is a document for PGroonga 2.X and 3.X. See PGroonga 1.x document when you're using old PGroonga.

pgroonga_list_lagged_indexes function

Since 3.2.1.

Summary

pgroonga_list_lagged_indexes function display a index of PGroonga with unapplied PGroonga WAL (not PostgreSQL WAL).

Specifically, it displays the following cases:

  1. If current_* and last_* in pgroonga_wal_status function are different

    • Displays the applicable PGroonga indexes

  2. If flushed_lsn and latest_end_lsn* in pg_stat_wal_receiver are different

    • Displays all PGroonga indexes

Syntax

Here is the syntax of this function:

SETOF text pgroonga_list_lagged_indexes()

It gets the index of PGroonga with unapplied PGroonga WAL (not PostgreSQL WAL).

It returns the following records:

 pgroonga_list_lagged_indexes
------------------------------
 pgrn_memos_index
 pgrn_tags_index

Usage

SELECT pgroonga_list_lagged_indexes();

Example

It is assumed that streaming replication and pgroonga.enable_wal = yes have already been set up.

Run in primary

CREATE TABLE memos (
  content text
);
CREATE TABLE tags (
  name text
);
CREATE INDEX pgrn_memos_index ON memos USING PGroonga (content);
CREATE INDEX pgrn_tags_index ON tags USING PGroonga (name);

Run in standby

PGroonga WAL not applied:

SELECT name,
       current_block,
       current_offset,
       current_size,
       last_block,
       last_offset,
       last_size
  FROM pgroonga_wal_status();
       name       | current_block | current_offset | current_size | last_block | last_offset | last_size 
------------------+---------------+----------------+--------------+------------+-------------+-----------
 pgrn_memos_index |             0 |              0 |            0 |          1 |         566 |      8758
 pgrn_tags_index  |             0 |              0 |            0 |          1 |         560 |      8752
(2 rows)

SELECT pgroonga_list_lagged_indexes();
 pgroonga_list_lagged_indexes
------------------------------
 pgrn_memos_index
 pgrn_tags_index
(2 rows)

PGroonga WAL already applied in some PGroonga indexes:

SELECT * FROM tags WHERE name &@ 'dummy';
 name
------
(0 rows)

SELECT name,
       current_block,
       current_offset,
       current_size,
       last_block,
       last_offset,
       last_size
  FROM pgroonga_wal_status();
       name       | current_block | current_offset | current_size | last_block | last_offset | last_size
------------------+---------------+----------------+--------------+------------+-------------+-----------
 pgrn_memos_index |             0 |              0 |            0 |          1 |         566 |      8758
 pgrn_tags_index  |             1 |            560 |         8752 |          1 |         560 |      8752
(2 rows)

SELECT pgroonga_list_lagged_indexes();
 pgroonga_list_lagged_indexes
------------------------------
 pgrn_memos_index
(1 row)

PGroonga WAL is applied to all PGroonga indexes:

SELECT pgroonga_wal_apply();
 pgroonga_wal_apply
--------------------
                  7
(1 row)

SELECT name,
       current_block,
       current_offset,
       current_size,
       last_block,
       last_offset,
       last_size
  FROM pgroonga_wal_status();
       name       | current_block | current_offset | current_size | last_block | last_offset | last_size
------------------+---------------+----------------+--------------+------------+-------------+-----------
 pgrn_memos_index |             1 |            566 |         8758 |          1 |         566 |      8758
 pgrn_tags_index  |             1 |            560 |         8752 |          1 |         560 |      8752
(2 rows)

SELECT pgroonga_list_lagged_indexes();
 pgroonga_list_lagged_indexes
------------------------------
(0 rows)

See also