trace_sort

• 18
• 17
• 16
• 15
• 14
• 13
• 12
• 11
• 10
• 9.6
• 9.5
• 9.4
• 9.3
• 9.2
• 9.1
• 9.0
• 8.4
• 8.3
• 8.2

trace_sort 的基本用法示例

postgres=# SET trace_sort TO on;
SET

postgres=# SELECT * FROM foo ORDER BY id desc limit 5;
  id   
-------
 10000
  9999
  9998
  9997
  9996
(5 rows)

PostgreSQL 日志文件将包含类似于以下内容的条目

[2023-12-11 16:50:09 UTC] psql postgres postgres LOG:  statement: SET trace_sort TO on;
[2023-12-11 16:50:11 UTC] psql postgres postgres LOG:  statement: SELECT * FROM foo ORDER BY id desc limit 5;
[2023-12-11 16:50:11 UTC] psql postgres postgres LOG:  begin datum sort: workMem = 4096, randomAccess = f
[2023-12-11 16:50:11 UTC] psql postgres postgres STATEMENT:  SELECT * FROM foo ORDER BY id desc limit 5;
[2023-12-11 16:50:11 UTC] psql postgres postgres LOG:  switching to bounded heapsort at 11 tuples: CPU: user: 0.00 s, system: 0.00 s, elapsed: 0.00 s
[2023-12-11 16:50:11 UTC] psql postgres postgres STATEMENT:  SELECT * FROM foo ORDER BY id desc limit 5;
[2023-12-11 16:50:11 UTC] psql postgres postgres LOG:  performsort of worker -1 starting: CPU: user: 0.00 s, system: 0.00 s, elapsed: 0.00 s
[2023-12-11 16:50:11 UTC] psql postgres postgres STATEMENT:  SELECT * FROM foo ORDER BY id desc limit 5;
[2023-12-11 16:50:11 UTC] psql postgres postgres LOG:  performsort of worker -1 done: CPU: user: 0.00 s, system: 0.00 s, elapsed: 0.00 s
[2023-12-11 16:50:11 UTC] psql postgres postgres STATEMENT:  SELECT * FROM foo ORDER BY id desc limit 5;
[2023-12-11 16:50:11 UTC] psql postgres postgres LOG:  internal sort of worker -1 ended, 25 KB used: CPU: user: 0.00 s, system: 0.00 s, elapsed: 0.00 s
[2023-12-11 16:50:11 UTC] psql postgres postgres STATEMENT:  SELECT * FROM foo ORDER BY id desc limit 5;

• PostgreSQL文档： trace_sort