Postgres 解释分析在 pgAdmin 中花费的负时间
Postgres explain analyze negative time spent in pgAdmin
我 运行 使用 pgAdmin 对我的 postgres 数据库进行解释分析查询。
它创建了一个独占时间为负的可视化：
我认为“Gather Merge”的总时间低于其子“Group”，但如果我正确阅读了原始 postgres 输出，则事实并非如此。
[
{
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]
这有什么合理的解释吗？ pgAdmin 可视化可以信任吗？
有一个类似的问题，但我没有看到那里解释了负值。
PostgreSQL 13.3 on aarch64-unknown-linux-gnu，由 gcc (GCC) 7.3.1 20180712 (Red Hat 7.3.1-6) 编译，64 位
PgAdmin 4.16
这是一个 pgAdmin 错误
pgAdmin 盲目地将执行时间与循环计数相乘，这对于嵌套循环来说没问题，但对于并行操作来说是错误的。所以“聚集”下面的数字高了三倍。
我 运行 使用 pgAdmin 对我的 postgres 数据库进行解释分析查询。
它创建了一个独占时间为负的可视化：
我认为“Gather Merge”的总时间低于其子“Group”，但如果我正确阅读了原始 postgres 输出，则事实并非如此。
[
{
"Plan": {
"Node Type": "Result",
"Parallel Aware": false,
"Startup Cost": 5259558.14,
"Total Cost": 5259558.24,
"Plan Rows": 1,
"Plan Width": 2,
"Actual Startup Time": 2891.076,
"Actual Total Time": 2925.989,
"Actual Rows": 1,
"Actual Loops": 1,
"Output": [
"(SubPlan 2)",
"(SubPlan 3)"
],
"Shared Hit Blocks": 16,
"Shared Read Blocks": 605065,
"Shared Dirtied Blocks": 0,
"Shared Written Blocks": 0,
"Local Hit Blocks": 0,
"Local Read Blocks": 0,
"Local Dirtied Blocks": 0,
"Local Written Blocks": 0,
"Temp Read Blocks": 0,
"Temp Written Blocks": 0,
"I/O Read Time": 1329.432,
"I/O Write Time": 0,
"Plans": [
{
"Node Type": "Group",
"Parent Relationship": "InitPlan",
"Subplan Name": "CTE foo",
"Parallel Aware": false,
"Startup Cost": 5255772.15,
"Total Cost": 5259558.14,
"Plan Rows": 4,
"Plan Width": 2,
"Actual Startup Time": 2851.957,
"Actual Total Time": 2925.973,
"Actual Rows": 3,
"Actual Loops": 1,
"Output": [
"\"DailyRatePricingTable\".\"HasFlatPrices\"",
"\"DailyRatePricingTable\".\"HasOccupancyPrices\""
],
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{
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{
"Node Type": "Bitmap Index Scan",
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"Index Cond": "(\"DailyRatePricingTable\".\"TenantId\" = '3eb2f28c-67aa-405d-9821-c9fc59de1501'::uuid)",
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}
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},
{
"Node Type": "CTE Scan",
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"CTE Name": "foo",
"Alias": "foo",
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"foo.\"HasFlatPrices\""
],
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},
{
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"Planning": {
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]
这有什么合理的解释吗？ pgAdmin 可视化可以信任吗？
有一个类似的问题
PostgreSQL 13.3 on aarch64-unknown-linux-gnu，由 gcc (GCC) 7.3.1 20180712 (Red Hat 7.3.1-6) 编译，64 位
PgAdmin 4.16
这是一个 pgAdmin 错误
pgAdmin 盲目地将执行时间与循环计数相乘，这对于嵌套循环来说没问题，但对于并行操作来说是错误的。所以“聚集”下面的数字高了三倍。