【发布时间】：2017-11-26 15:25:41
【问题描述】：
我有以下查询（postgresql）：
select prt.a,
(SELECT count(ind.b) FROM ind WHERE ind.indexed_field_1 @@ to_tsquery(prt.a)
AND lower(ind.t) not in ('a', 'b', 'c')) cnt
from p as prt
order by cnt desc
limit 200;
ind.indexed_field_1 使用 GIN 索引进行索引。到目前为止一切顺利 - 它大约运行了约 1 秒（ind 有约 600K 行）。
一旦我将indexed_field_2 添加到ind 表中，并使用 GIN 索引对其进行索引 - 原始查询突然运行约 5 秒，indexed_field_2 上的类似查询也是如此：
select prt.a,
(SELECT count(ind.b) FROM ind WHERE ind.indexed_field_2 @@ to_tsquery(prt.a)
AND lower(ind.t) not in ('a', 'b', 'c')) cnt
from p as prt
order by cnt desc
limit 200;
有什么线索会导致这种情况吗？
执行计划看起来一样。
编辑：
第二次查询的执行计划：
[
{
"Execution Time": 4863.615,
"Planning Time": 0.3,
"Plan": {
"Startup Cost": 383480149.03,
"Shared Hit Blocks": 1296773,
"Shared Written Blocks": 0,
"Shared Read Blocks": 267565,
"Plans": [
{
"Temp Written Blocks": 0,
"Sort Key": [
"((SubPlan 1)) DESC"
],
"Node Type": "Sort",
"Sort Space Used": 46,
"Shared Hit Blocks": 1296773,
"Plans": [
{
"Node Type": "Seq Scan",
"Shared Hit Blocks": 1296773,
"Plans": [
{
"Partial Mode": "Simple",
"Node Type": "Aggregate",
"Strategy": "Plain",
"Shared Hit Blocks": 1296773,
"Subplan Name": "SubPlan 1",
"Plans": [
{
"Exact Heap Blocks": 1383693,
"Node Type": "Bitmap Heap Scan",
"Shared Hit Blocks": 1296773,
"Plans": [
{
"Startup Cost": 0,
"Plan Width": 0,
"Temp Written Blocks": 0,
"Shared Written Blocks": 0,
"Shared Read Blocks": 5872,
"Local Written Blocks": 0,
"Node Type": "Bitmap Index Scan",
"Index Cond": "(indexed_field_2 @@ to_tsquery(prt.a)",
"Plan Rows": 3156,
"Temp Read Blocks": 0,
"Shared Dirtied Blocks": 0,
"Local Hit Blocks": 0,
"Parallel Aware": false,
"Actual Rows": 51,
"Local Dirtied Blocks": 0,
"Parent Relationship": "Outer",
"Total Cost": 43.68,
"Shared Hit Blocks": 173739,
"Actual Loops": 44742,
"Local Read Blocks": 0,
"Index Name": "part_ids2_idx"
}
],
"Shared Read Blocks": 266531,
"Relation Name": "ind",
"Local Hit Blocks": 0,
"Local Dirtied Blocks": 0,
"Temp Written Blocks": 0,
"Plan Width": 16,
"Actual Loops": 44742,
"Rows Removed by Index Recheck": 0,
"Lossy Heap Blocks": 0,
"Filter": "(lower(ind.t) <> ALL ('{a,b,c}'::text[]))",
"Alias": "ind",
"Recheck Cond": "(indexed_field_2 @@ to_tsquery(prt.a)",
"Temp Read Blocks": 0,
"Local Read Blocks": 0,
"Startup Cost": 44.46,
"Shared Dirtied Blocks": 0,
"Shared Written Blocks": 0,
"Local Written Blocks": 0,
"Plan Rows": 3109,
"Parallel Aware": false,
"Actual Rows": 51,
"Parent Relationship": "Outer",
"Total Cost": 8563.06,
"Rows Removed by Filter": 0
}
],
"Shared Read Blocks": 266531,
"Temp Written Blocks": 0,
"Local Dirtied Blocks": 0,
"Local Hit Blocks": 0,
"Plan Width": 8,
"Actual Loops": 44742,
"Temp Read Blocks": 0,
"Local Read Blocks": 0,
"Startup Cost": 8570.83,
"Shared Dirtied Blocks": 0,
"Shared Written Blocks": 0,
"Local Written Blocks": 0,
"Plan Rows": 1,
"Parallel Aware": false,
"Actual Rows": 1,
"Parent Relationship": "SubPlan",
"Total Cost": 8570.84
}
],
"Shared Read Blocks": 267565,
"Relation Name": "parties",
"Temp Written Blocks": 0,
"Local Dirtied Blocks": 0,
"Local Hit Blocks": 0,
"Plan Width": 24,
"Actual Loops": 1,
"Alias": "parties",
"Temp Read Blocks": 0,
"Local Read Blocks": 0,
"Startup Cost": 0,
"Shared Dirtied Blocks": 0,
"Shared Written Blocks": 0,
"Local Written Blocks": 0,
"Plan Rows": 44742,
"Parallel Aware": false,
"Actual Rows": 44742,
"Parent Relationship": "Outer",
"Total Cost": 383478215.31
}
],
"Shared Read Blocks": 267565,
"Local Hit Blocks": 0,
"Local Dirtied Blocks": 0,
"Sort Method": "top-N heapsort",
"Plan Width": 24,
"Actual Loops": 1,
"Temp Read Blocks": 0,
"Local Read Blocks": 0,
"Shared Written Blocks": 0,
"Startup Cost": 383480149.03,
"Shared Dirtied Blocks": 0,
"Sort Space Type": "Memory",
"Local Written Blocks": 0,
"Plan Rows": 44742,
"Parallel Aware": false,
"Actual Rows": 200,
"Parent Relationship": "Outer",
"Total Cost": 383480260.89
}
],
"Local Written Blocks": 0,
"Node Type": "Limit",
"Plan Rows": 200,
"Temp Read Blocks": 0,
"Shared Dirtied Blocks": 0,
"Local Hit Blocks": 0,
"Parallel Aware": false,
"Actual Rows": 200,
"Local Dirtied Blocks": 0,
"Temp Written Blocks": 0,
"Plan Width": 24,
"Actual Loops": 1,
"Local Read Blocks": 0,
"Total Cost": 383480149.53
},
"Triggers": []
}
]
【问题讨论】：
标签： postgresql indexing full-text-search