sql-execution-plan Questions

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Based on getting Query Execution Statistics using this extremely useful piece of SQL obtained from this post Most Executed Stored Procedure - Stack Overflow: SELECT TOP 100 qt.TEXT AS 'SP Name', ...
Ginsberg asked 11/2, 2010 at 9:55

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I have a view in SQL Server that calls a function. When I show the actual execution plan for querying the view, what happens inside the function is completely opaque though. As a small example, I m...
Peril asked 10/3, 2023 at 8:48

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I have SQL Server installed on Linux. It was installed from Microsoft's repos as described here: https://learn.microsoft.com/en-us/sql/linux/quickstart-install-connect-ubuntu In MySql I used to wr...

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I am looking at the actual execution plan of SELECT * FROM dbo.Parcels pr WHERE (pr.Barcode = 'AB123456789DE') and the actual execution plan contains an operator (index seek nonclustered) which ...
Big asked 20/12, 2023 at 12:42

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The MySQL 5.7 documentation states: The filtered column indicates an estimated percentage of table rows that will be filtered by the table condition. That is, rows shows the estimated number of ...
Towny asked 8/1, 2017 at 16:16

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I'm reading "Dissecting SQL Server Execution Plans" from Grant Fritchey and it's helping me a lot to see why certain queries are slow. However, I am stumped with this case where a simple rewrite p...
Couplet asked 28/2, 2012 at 14:46

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Does PostgreSQL cache execution plan of a view, as it does for stored procedures?
Illicit asked 16/9, 2014 at 9:14

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From time to time I encounter a strange MySQL behavior. Let's assume I have indexes (type, rel, created), (type), (rel). The best choice for a query like this one: SELECT id FROM tbl WHERE rel = 3...
Biramous asked 24/12, 2010 at 13:52

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The problem Using PostgreSQL 13, I ran into a performance issue selecting the highest id from a view that joins two tables, depending on the select statement I execute. Here's a sample setup: CREAT...

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How can I measure execution time of query in MongoDB ? I found Mongo-hacker plugin but it looks like it measure time of query including time of displaying all results. In PostgreSQL I use Explain A...
Eaglestone asked 15/4, 2016 at 13:32

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I have a strange problem with PostgreSQL performance for a query, using PostgreSQL 8.4.9. This query is selecting a set of points within a 3D volume, using a LEFT OUTER JOIN to add a related ID col...

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In Microsoft SQL Server how can I get a query execution plan for a query / stored procedure?
Coreen asked 9/9, 2011 at 9:37

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Just a general question: Is there a query/command I can pass to SQL Server not to use cache when executing a particularly query? I am looking for a query/command that I can set rather than a conf...
Lave asked 6/12, 2009 at 23:14

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What is the meaning of Select tables optimized away in MySQL Explain plan? explain select count(comment_count) from wp_posts; +----+-------------+---------------------------+--------------------...
Endstopped asked 2/1, 2010 at 18:18

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This is my sample query Select table1.id from table1 where table.id in (select table2.id from table2 where table2.id in (select table3.id from table3) ) order by table1.id limit 100 On ...
Subtotal asked 13/12, 2020 at 14:19

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Consider a table with two non clustered index, and query: 1 INDEX_1 on table (column1, column2, column3) 2 INDEX_2 on table (column1) INCLUDED (column2, column3) SELECT column3 FROM table WHERE...
Annihilation asked 26/10, 2020 at 17:34

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I've a stored procedure that does something like this: SELECT Id INTO #temp FROM table WHERE ... DELETE FROM #temp INNER JOIN table2 ON a=b WHERE ... But it's running slowly. When I try to view...
Eolic asked 11/1, 2012 at 16:29

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Can anyone explain me what is the difference between execution plan and explain plan. When I execute set autotrace traceonly; select * from emp where empno=7369; Execution Plan --------------...
Blub asked 13/5, 2012 at 14:44

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According to the MySQL documentation, Using where means: A WHERE clause is used to restrict which rows to match against the next table or send to the client. As I understand, it means if your sql s...
Selfpollination asked 17/7, 2020 at 5:6

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I have a query that fails to execute with "Could not allocate a new page for database 'TEMPDB' because of insufficient disk space in filegroup 'DEFAULT'". On the way of trouble shooting I am exam...
Grenadier asked 11/8, 2015 at 18:28

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I am little bit confused and need some advice. I use PostgreSQL 11 database. I have such pretty simple sql statement: SELECT DISTINCT "CITY", "AREA", "REGION" FROM youtube WHERE "CITY" IS NOT NU...

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Suppose I want to query a big table with a few WHERE filters. I am using Postgres 11 and a foreign table; foreign data wrapper (FDW) is clickhouse_fdw. But I am also interested in a general solutio...

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Is there any proper resource from where we can understand explain plan generated by hive completely? I have tried searching it in the wiki but could not find a complete guide to understand it. Here...
Aneroidograph asked 11/6, 2018 at 7:58

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I have few SQL queries which has very low query running performance and I want to check the query execution plan for this query. I am trying to execute the below query but its not showing any query...
Oxpecker asked 6/5, 2015 at 8:3

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Please answer,thanks a lot. Q1: why is the query condition a.id = b.id but only scanned the index of a.id at the beginng? but the number of loop is so big ? Q2: What does the 'Nested Loop' node d...
Deist asked 13/2, 2020 at 15:17

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