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Questions tagged [execution-plan]

The strategy selected by the query optimizer to process a query.

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Trying to optimize an aggregrate query for a big table in postgres

I'm trying to retrieve to get a top 3 of players from a big database containing their stats. To do this i want to sum the kills they got in all of their games and select the 3 that have the most kills....
Bijleveldje's user avatar
1 vote
1 answer
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Filter out rows where any value is not unique

I am self joining on a table and get the following result: +----+----+----+----+----+----+----+----+----+ | id | s1 | s2 | s3 | s4 | s5 | s6 | s7 | s8 | +----+----+----+----+----+----+----+----+----+ |...
Some_user's user avatar
1 vote
2 answers
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Simple query with two WHERE clauses uses inferior index scan

I have a table named "db_log" with a size of 11GB and approximately 10 million rows in PostgreSQL 13.7 version. The issue is that a simple query is not performing an full index scan for ...
Rio Fajar's user avatar
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Why the second query is so much faster than the first one?

I have a query that look like this: SELECT DISTINCT "articles"."id", "articles"."company_uuid", "articles"."status", "articles&...
Mio's user avatar
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12 votes
2 answers
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Unable to execute query and not even able to generate Estimated execution plan

I am working on SQL Server 2019. I have a table dbo.AllDates where I have all dates from 1990 to 2050. I have another table dbo.ActualExchangeRates where I have actual exchange rates for certain ...
saadkaul's user avatar
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3 votes
1 answer
211 views

How does SQL Server estimate cardinality on nested loops index seek

I am trying to understand how SQL Server estimates cardinality on the below Stack Overflow database query Firstly, I create the index CREATE INDEX IX_PostId ON dbo.Comments ( PostId ) INCLUDE ( ...
SE1986's user avatar
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1 vote
1 answer
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MySQL explain plan doesn't show key lookup

I have a query that's really slow when I select a lot of columns but greatly speeds up when I only select the columns present in the index the query is using. This makes me believe that the query is ...
Archmede's user avatar
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6 votes
3 answers
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Is there an option or hint possible to improve performance of query with multiple values in the "in" clause

We have a table CustomerNote with 4 columns ID, CustomerID, Note, Date There is an index on CustomerID asc, Date desc When the following query is executed select top 30 Date from CustomerNote ...
MichaelD's user avatar
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0 answers
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Compile time of update query is high on sqlserver 2019 vs sqlserver 2016

A dev team announced performance degradation after migrating their database from SQLServer 2016 to SQLServer 2019. So I started tracing the database using SQL profiler. It turns out duration, cpu ...
Peter Mobiel's user avatar
1 vote
2 answers
68 views

Is it possible to save the statistics profile result into a table?

In SQL Server, we can use set statistics profile on to enable profiling for a session. Then you can execute any statement and the corresponding execution plan will be shown in a tabular form. Is it ...
Fajela Tajkiya's user avatar
-1 votes
1 answer
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What causes a stored procedure to have multiple plans in SQL Server?

We have noticed that many of our stored procedures, which involve the use of local variables, have multiple plans associated with them. By which I mean the same query in the stored procedure has ...
lifeisajourney's user avatar
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Stored procedure suddenly using multiple execution plans in SQL Server 2012

We have a commonly utilized stored procedure that had been functioning properly, but it unexpectedly began utilizing several plans (as many as 20, according to the performance analyzer) and causing a ...
JoeCharles's user avatar
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1 answer
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How to efficiently get absolute value of a time interval in Postgresql?

I have a huge table in Postgresql-11 like following: CREATE TABLE my_huge_table( tick_time timestamp(6) with time zone NOT NULL, brok_time timestamp(6) with time zone, trade_day date NOT ...
Leon's user avatar
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1 answer
42 views

PostgreSQL: Unwanted materialize node within nested loop join

I have a peculiar situation where PostgreSQL is choosing to materialize rather than use a particular index I've created for a query where I join a generate_series() against a table storing streamed ...
shangxiao's user avatar
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4 answers
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Window function with subquery results to unexpectedly slow query plan

This is my victim query SELECT *, lag(quantity) over (partition by product_id, size_id, warehouse_id order by size_id, warehouse_id, created_at ASC) - quantity as orders FROM ...
glmn's user avatar
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2 votes
3 answers
292 views

EXPLAIN ANALYZE does not show what takes time with my GIN index scan

Context I have a table named companies_establishments that holds ~33M rows. I created a GIN index with trigrams, so I can make LIKE queries much faster. CREATE INDEX companies_establishments_id_index ...
Madeorsk's user avatar
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4 votes
1 answer
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SQL Server generates a query plan with parallelism and TOP statement

I have two simple queries: SELECT TOP(20) * FROM Clients ORDER BY City SELECT TOP(20) Id, Name, City FROM Clients ORDER BY City In the first case I get a result like this Id Name City many more ...
Bert de Saffel's user avatar
1 vote
2 answers
122 views

Query Store plan does not include parameter list

I use the query store to get an overview of executed queries on our databases and to generate performance tests where I execute those queries in parallel on multiple hosts. My task is to test how many ...
SteLoe's user avatar
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2 votes
0 answers
162 views

Postgres: One-to-many relationship with WHERE, ORDER BY and LIMIT not scalable?

I'm currently using Postgres 12. A few years ago, I set up the following model: a lot table with a one-to-many relationship to a line table. My idea was to mutualize data that are common for multiple ...
K.Banks's user avatar
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1 answer
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Query using VIEW very slow when the same query is fast using WITH

Given this view CREATE OR REPLACE VIEW public."SellMeta" AS WITH wh AS ( SELECT "WWHH".id, "WWHH".url, "WWHH".name, ...
Fabiano Taioli's user avatar
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1 answer
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Help me in optimising the query which takes almost 50 seconds

Please help me optimise the following query running on MySQL 8.0.28 Community Edition. explain select id, created_at, data, deleted_at, entity_id, ...
Avinash Pawar's user avatar
6 votes
1 answer
533 views

How to reduce query size with many repeated UNION subqueries?

I use Postgres 13 and have a table defined with the following DDL: CREATE TABLE item_codes ( code bytea NOT NULL, item_id bytea NOT NULL, time ...
Vitalii Vitrenko's user avatar
3 votes
1 answer
578 views

How To Optimize a Query That Aggregates Then Duplicates a Large Number of Records in a Single Table

In the following post, J.D. brings up that I have a poorly performing query. I am running this query on SQL Server 2019 Standard Edition (query plan was generated in Development Edition) Let's take a ...
David Rogers's user avatar
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PostgreSQL query times out when selecting a smaller amount of data (different query plan)

PostgreSQL 15.2. We have a table like this (simplified): create table behavior.event_59 ( event_id integer not null primary key, second_offset integer not null, -- ... more columns ) ...
EM0's user avatar
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1 vote
0 answers
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How to reduce high cost of sort on execution plan

I have a very large query with three UNION ALL and it takes 30 minutes to execute. Analyzing the execution plan I see that it has a high cost in SORT and Filter. I tried to generate the showplan in ...
Carlos D's user avatar
10 votes
1 answer
1k views

SELECT Statement with , * in column list is faster than same statement without *

Situation When querying a database with a SELECT statement with a defined set of columns, the results are received in around 21 seconds. If there is an additional asterisk (, *) at the end of the list ...
John K. N.'s user avatar
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3 votes
1 answer
120 views

Improving query response speed when joining a non-spatial table with a spatial table on a non-spatial column

I have a table of frequently updating events that affect certain geometries. The geometry areas are fixed, but there may be an event affecting multiple areas at once, so there's a many-to-many ...
wxdan's user avatar
  • 33
1 vote
2 answers
139 views

Lots of "key value" joins causes SQL Server query to exponentially slow down

I am migrating some data that's stored "key value" style, from an attributes table that uses an Object ID and an Attribute Type as a Clustered Index (I've also tried as a nonclustered index):...
Thomas's user avatar
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0 votes
1 answer
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What makes the optimizer insert a sort operator in the plan

What are the reasons that the optimizer chooses to insert a sort operator in the plan (to satisfy a stream aggregate or a merge join, etc.) instead of going for hash match or hash join? I have now see ...
xhr489's user avatar
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Hierarchical query to select `children` from `children`

I have the following table mytable where id is a unique identifier at a given r (resolution) and children is an array of unique id's of r + 1. id r children[] 0 2 {0,2467972595799031808,...
Michael's user avatar
  • 263
2 votes
0 answers
17 views

set options for replicating slow queries in SSMS

I am investigating a slow ad-hoc query(about 45 seconds) from our application. I am not able to replicate the slowness in ssms however to investigate indexing, reads, etc. I've attempted to use the ...
DBA Greg14's user avatar
1 vote
0 answers
23 views

Improve cardinality estimation when two joined tables have a condition on an identical column

I have a table foo, with an association table foo_associations with columns foo_parent and foo_child. foo has an column called department_id. Any association made through foo_associations is ...
Joe's user avatar
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0 answers
80 views

Why is Live Query Plan not available on my SQL Server 2019?

Based on this article on Query Profiling Infrastructure SQL Server 2019 should have the lightweight profiling infrastructure v3 enabled by default. However, when I try to display Live Execution Plan, ...
Timbalero's user avatar
2 votes
1 answer
210 views

Why changing limit triggers different query plans in postgresql?

Changing only limit from 40 to 50 in following query triggers different execution plans. And unfortunatly one I needed is much slower. So the question is: why this happening and how can I force ...
Gor Rustamyan's user avatar
1 vote
1 answer
63 views

Postgresql - long column select/projection list leads to poor performance

I have a rather structurally "simple" query that consists basically in these clauses: SELECT [650 columns here] FROM MAIN_TABLE (Several Joins) WHERE (Some conditions in ...
J.Hudler's user avatar
  • 155
6 votes
1 answer
469 views

Why does SQL Server sometimes estimate that joining onto an empty table will increase the row count?

I recently came across an issue where tSQLt tests were taking a long time to run. The procedure under test was doing a 38 table (!) join (with 37 faked tables and a table valued parameter). Only two ...
Martin Smith's user avatar
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0 votes
0 answers
217 views

How to avoid cluster index scan?

I've a table with a few millions of records. Here's the table structure: Column_name Type Computed Length Prec Scale Nullable TrimTrailingBlanks FixedLenNullInSource Collation Id int no 4 10 0 no (n/...
Thomas Ayoub's user avatar
1 vote
1 answer
97 views

Using btree index with LIKE operator but not equal (=)

In summary, Postgres prefers doing the equivalent of a [datetime index seqscan]+[filter (using the heavy function)] instead of using the index when using = to find what I like. When simply replacing = ...
TiCPU's user avatar
  • 113
1 vote
2 answers
121 views

PostgreSQL WHERE IS NULL causes bad query plan

I have a PostgreSQL table with the following schema and indexes +---------+---------+-----------+----------+--------------+-------------+ | Column | Type | Modifiers | Storage | Stats target | ...
nick314's user avatar
  • 117
5 votes
1 answer
310 views

How to optimize PostgreSQL OR query on two indexed columns

I have a large partitioned table that stores monetary transactions between accounts. CREATE TABLE "transactions" ( "from" BYTEA NOT NULL -- sender account ,"to&...
nick314's user avatar
  • 117
0 votes
1 answer
29 views

Can Postgresql FDW avoid n+1 when planning joins?

Does the PostgreSQL executor / planner have the ability to avoid n+1 querying of FDW tables? If so, what conditions have to be in place for this to happen, e.g. does the FDW need to emit a specific ...
ldrg's user avatar
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0 votes
0 answers
151 views

Force Microsoft SQL to recreate and use Specific execution plan?

I have a stored procedure that was working really well for about 3 weeks, than all of a sudden it basically ground to a complete Stop. This was i believe due to the server creating an additional query ...
Praxiom's user avatar
  • 101
0 votes
1 answer
45 views

Enforce query plan for queries with expensive predicates/UDFs

I have a question on how to enforce the query optimizer to use a certain execution plan. Lets assume we have two tables, t1 (25k rows) and t2 (100k rows). Also note that all the rows in t1 will find ...
KSV97's user avatar
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0 votes
0 answers
70 views

Computed column marked as PERSISTED still calculates every time [duplicate]

I have the following table: CREATE TABLE dbo.Cases ( CaseCaption nvarchar(255), NickNameComputed AS (dbo.fn_ParseNickName(CaseCaption)) NOT NULL, NickNamePersisted AS (dbo.fn_ParseNickName(...
AngryHacker's user avatar
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1 vote
1 answer
89 views

Testing the estimated query plan of a portion of a trigger that uses inserted/deleted

I'm performance tuning a SQL Server trigger that has several statements using the "inserted" and "deleted" tables. How can I break out those individual queries from the trigger for ...
skeletank's user avatar
  • 301
3 votes
1 answer
216 views

Query store plan is not forcing and there is no failure reason [duplicate]

I have forced a plan in query store as follows EXEC sys.sp_query_store_force_plan @query_id = 113366, @plan_id = 3687662 but when I run the query again, the query does not use the plan, nor does it ...
SE1986's user avatar
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0 votes
0 answers
11 views

Is it possible to view the execution plan in RethinkDB?

I've been looking online to see if I could find anything on seeing the actual execution plan on RethinkDB, but it doesn't seem to be possible. Their website says sort of how it works, but not if it is ...
telometto's user avatar
  • 101
4 votes
2 answers
219 views

Execution plan - reading more records than in table

SQL newbie here, so apologies if this is pretty basic stuff. SQL server 2019, Windows 2 tables - FixingHeader and Product Simple query reading all fixing header and find related product select [f].[...
OEDev's user avatar
  • 49
0 votes
1 answer
122 views

ANALYZE or EXPLAIN for previous query

EXPLAIN SELECT ... shows the EXPLAIN for a query (without actually running it). SHOW EXPLAIN FOR conn_id shows the EXPLAIN for a query that is currently running. Is it possible to get the EXPLAIN for ...
Nuno's user avatar
  • 758
0 votes
0 answers
22 views

Local variables and their impact on execution plans in SQL Server Stored Procedure [duplicate]

If a parameter that is passed to stored procedure is assigned to a local variable and the local variable is used inside the stored procedure logic, will that affect the execution plan in any way? Is ...
lifeisajourney's user avatar

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