log_autovacuum_min_duration

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• 8.3

为了演示 log_autovacuum_min_duration 的效果，创建一个表，并将 存储参数 设置为在少量插入操作后触发自动清理

postgres=# CREATE TABLE foo (id INT) WITH (
    log_autovacuum_min_duration = 0,
    autovacuum_vacuum_insert_threshold = 5);
CREATE TABLE

postgres=# INSERT INTO foo VALUES (generate_series(1,10));
INSERT 0 10

这（假设自动清理守护程序没有其他占用）将在短时间内导致自动清理操作，并将以以下方式记录（使用 track_io_timing 设置为默认值 off）

[2021-12-14 08:13:26 UTC]    LOG:  00000: automatic vacuum of table "postgres.public.foo": index scans: 0
        pages: 0 removed, 1 remain, 0 skipped due to pins, 0 skipped frozen
        tuples: 0 removed, 10 remain, 0 are dead but not yet removable, oldest xmin: 740
        index scan not needed: 0 pages from table (0.00% of total) had 0 dead item identifiers removed
        avg read rate: 27.174 MB/s, avg write rate: 27.174 MB/s
        buffer usage: 55 hits, 4 misses, 4 dirtied
        WAL usage: 5 records, 4 full page images, 33264 bytes
        system usage: CPU: user: 0.00 s, system: 0.00 s, elapsed: 0.00 s

使用 [track_io_timing|]] 设置为 on

[2021-12-14 08:17:34 UTC]    LOG:  00000: automatic vacuum of table "postgres.public.foo": index scans: 0
        pages: 0 removed, 1 remain, 0 skipped due to pins, 0 skipped frozen
        tuples: 0 removed, 30 remain, 0 are dead but not yet removable, oldest xmin: 751
        index scan not needed: 0 pages from table (0.00% of total) had 0 dead item identifiers removed
        I/O timings: read: 0.000 ms, write: 0.000 ms
        avg read rate: 0.000 MB/s, avg write rate: 135.281 MB/s
        buffer usage: 31 hits, 0 misses, 4 dirtied
        WAL usage: 5 records, 5 full page images, 34920 bytes
        system usage: CPU: user: 0.00 s, system: 0.00 s, elapsed: 0.00 s

• PostgreSQL 文档： log_autovacuum_min_duration