mirror of
https://github.com/timescale/timescaledb.git
synced 2025-05-22 13:40:56 +08:00
b7257fc8f4
This planner optimization reduces planning times when a hypertable has many chunks. It does this by expanding hypertable chunks manually, eliding the `expand_inherited_tables` logic used by PG. Slow planning time were previously seen because `expand_inherited_tables` expands all chunks of a hypertable, without regard to constraints present in the query. Then, `get_relation_info` is the called on all chunks before constraint exclusion. Getting the statistics an many chunks ends up being expensive because RelationGetNumberOfBlocks has to open the file for each relation. This gets even worse under high concurrency. This logic solves this by expanding only the chunks needed to fulfil the query instead of all chunks. In effect, it moves chunk exclusion up in the planning process. But, we actually don't use constraint exclusion here, but rather a variant of range exclusion implemented by HypertableRestrictInfo.
5 lines
170 B
SQL
5 lines
170 B
SQL
SET timescaledb.disable_optimizations= 'off';
|
|
\set PREFIX 'EXPLAIN (costs off) '
|
|
\ir include/plan_expand_hypertable_load.sql
|
|
\ir include/plan_expand_hypertable_query.sql
|