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

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2
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1answer
359 views

Does a change in a query executed with sp_executesql cause recompilations?

I am experiencing a lot of re-compilations in my database. Most of the queries being executed are simple queries and all of them are being executed using the sp_executesql stored procedure. ...
2
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0answers
47 views

Execution plan of query inside pl/pgsql function

Briefly, we have a pl/pgsql function which collects some intermediate data in several temporary tables ("on commit drop") and then returns REFCURSOR which joins those temporary tables with some static ...
2
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0answers
101 views

This Extended Events session works on Dev but not on Pro. Why? [closed]

I do have the following Extended Event session on my Dev and Pro boxes: CREATE EVENT SESSION [sp_showplan] ON SERVER ADD EVENT sqlserver.query_post_execution_showplan(SET collect_database_name=(1) ...
2
votes
1answer
159 views

High I/O for part of query

I have a large query that I'm trying to tune. I write lots of queries but haven't done a lot of tuning. I've included a screenshot from SQL Sentry Plan Explorer Free (SSPEF): In the above part of ...
2
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0answers
115 views

Multi-Statement Template Plan Guide

A piece of, um, software seems to be issuing ~20k queries of this form every few seconds: DELETE FROM macVendor WHERE companyId=N' 08-00-'; INSERT INTO macVendor (companyId,organization) VALUES (N' ...
2
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0answers
49 views

Identical query & instance but other execution plans & performance [duplicate]

I have 2 identical queries . One is executed with parameters, the other is executed with hardcoded values. Somehow sql server is creating 2 different execution plans for the 2 queries. The first one ...
2
votes
0answers
412 views

Oracle 11g bug ? not returning the record until I triggered index to invisible and then to visible

We are using Oracle 11g, 11.2.0.3. We know a record exists in a table but a select is not returning it for some odd reason. The execution plans the general query, not forcing any index, shows that ...
1
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1answer
182 views

Understanding execution plans using TVPs

I have some slow running queries (8 seconds across 1M records grouped by months) and have been trying to make sense of the execution plans. We use around 10 TVPs to send in a set of filters that the ...
1
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2answers
2k views

Updating a table efficiently using JOIN

I have a table that has the details of households and another that has the details of all the persons associated with the households. For the household table I have a primary key defined using two ...
1
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1answer
125 views

Estimated rows very wrong when using declared variables

I am getting very, very wrong estimates for the clustered index seek step of this query (estimated rows is 8,637,530; actual is 74,723): Declare @StartDate as date = '10/1/2014'; Declare @EndDate as ...
1
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3answers
2k views

Why would recompile query hint result in different plan for same adhoc statement after freeproccache?

This is on SQL 2005 SP2, but I suspect this is something that applies to all query hints in general. I've got an adhoc sql statement that gets a different query plan solely because of ...
1
vote
1answer
96 views

Query Plan Different When Using Compiled Values

I have pulled out an execution plan from the plan cache and from the XML pulled out the compiled values. Then I have run the query in SSMS using the compiled values and the query plans are different ...
1
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1answer
227 views

Relative cost of two similar queries involving XML columns

I have two queries as shown below which do the same thing. Here xmlcolumn is a column with datatype XML. I use these queries to search for a string anywhere in the XML column. I checked the execution ...
1
vote
1answer
136 views

SQl code performance

What measurement do you know if this sql code is efficient based on execution plans? How do you know if this sql code is efficient based on execution plans? SELECT [CustomerID], ...
1
vote
1answer
156 views

Understanding MySQL's 'explain'

I have following query with explain: mysql> explain select dd.data from dane dd join test1.tag1 t1 on dd.id = t1.id join test1.tag2 t2 on dd.id = t2.id join ...
1
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1answer
50 views

SQL Server 2012 Execution Plan

I was reading through Kendra Little's post on www.brentozar.com http://www.brentozar.com/archive/2013/08/query-plans-what-happens-when-row-estimates-get-high/ In the post, Kendra mentioned that she ...
1
vote
1answer
134 views

Execution Plan in Microsoft SQL Server

I have a stored procedure in my database. As per my knowledge it's pre-compiled subroutine. Question 1: If I execute following queries from Hibernate, will database create a separate execution plan ...
1
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1answer
69 views

Execution Plan : Table Insert Cost 90% vs Clustured Index Insert Cost 86% [duplicate]

Situation : We have table It has millions of records. Table has 1 Clustured Index and 1 Non Clustured Index. It was found that Clustured Index is not used by any of SQL Query. But Insert Execution ...
1
vote
1answer
202 views

Binding errors with dependent stored procedures

We are getting strange errors on one of our stored procedures. This stored procedure calls other stored procedures & we are getting errors relating to columns that cannot be found in the sub ...
1
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3answers
42 views

SQL actually executed as planned in ORACLE?

I wonder if SQL is definitely executed as execution plan. I mean.. is the actual SQL execution process always consistent with execution plan, i.e. does the same SQL always give the same plan?
1
vote
1answer
87 views

Query Plan showing missing index warning on trivial statements

I have a Stored Procedure (ReportAdvancedUP) which runs fast (~1sec) in MSSMS but takes a long time (~1.8mins) via our Web Application. I am aware that this usually comes down to bad choice of ...
1
vote
1answer
130 views

Deciding which MySQL execution plan is better

Background: I have a query that I'm trying to speed up, involving 3 tables: omgenvelope has 5 million rows omgcust has 195 rows omginput has 35836 rows I'm obtaining the distinct omginputs ...
1
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1answer
139 views

Print the execution time on messages Pane?

How I can print the execution time of each query on messages Pane? For example the Select * from tbl1 runs for 10 mins then Select * from tbl2 runs for 15mins and so on.. Select * from tbl1 Go Select ...
1
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1answer
4k views

Different execution plan for the same query if I change a value in the predicate

I am getting two different execution plans for the same query only by changing the value in the predicate, the first one uses nested loops and the other one hash join which takes a lot longer. ...
1
vote
1answer
101 views

A query executed in a backup of a database is performing better than if executed in the original database

We have two databases with the same data, let's call it Database A which is the original and Database B which is the backup from Database A. A query is performing much better in Database B for example ...
1
vote
2answers
168 views

Execution Plans Query

I want to check the estimated number of rows of a query in MS SQL Server. I can right click on the query and select "display estimated execution plan". but I want to do the exact thing with a hard ...
1
vote
1answer
63 views

Another bad execution plan!

This is running SQL Server 2012 SP2 Enterprise Edition. I have a nightly ETL job that, for a specific SP, is taking way too long to run. During my investigation I found that it was a specific update ...
1
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1answer
104 views

Reading a SQL Server Execution plan

I am very new to any type of tuning but have been learning more.. One of my specific databases one of the problems identified with slow queries are a number of Implicit conversions. It is my ...
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0answers
107 views

Different Execution Plans Picked for Similar Queries

Thank you in advance for reading it. This question is kind of long and need a little patience to read. I will provide as much details as I can to void interference factors to solve this problem. ...
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0answers
81 views

What to look for in query execution plans? [closed]

Assuming the query execution is slow, I have collected the xml plan. What should I look for in the actual execution plan. What are the top 10 things I need to watch out for? I know this is a broad ...
0
votes
2answers
35 views

why the optimizer doesn't choose the optimal plan [closed]

I know, if the statistic is not updatad, it is possible, that the optimizer doesn't choose the optimal execution plan? Does any other reason/reasons exist?
0
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1answer
98 views

How many LEFT JOINS make a VIEW unusable?

I have a view which involves LEFT JOINS on 20+ tables to a base table but when querying this view and looking at the execution plans I am getting something totally unexpected. For example, with the ...
0
votes
1answer
50 views

Viewing execution plans for queries with parameters

I have a sample query generated by an application (Microsoft Dynamics AX 2012 in this case) which is ineffective performance-wise (cross joins, order by etc.) I would like to display its execution ...
0
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1answer
82 views

Why the optimizer does not use an Index Unique Scan?

I am on Oracle 10.2.0.4.0. I have a big Index Organized Table (IOT) with 74 columns and over 345 million of rows. An external tool execute a batch where I cannot touch the source code. The critical ...
0
votes
1answer
212 views

Oracle 10g: same query, different plans on copies of the same DB

I have a query joining a number of long tables (primary key in one table, indexed column in another) which results in different plans on different copies of the same database. The structure of copies ...
0
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1answer
60 views

Access and filter in oracle plan

I came to a execution plan where oracle choose to access the index but instead of using the columns as predicate it only filter by them. My question is what are the reasons that can cause that(all ...
0
votes
1answer
156 views

Comparing execution plans [closed]

How does the optimizer compare different execution plans of the same query? Let's say we have two complex and structurally different execution plans, how can I know if they are providing the same ...
0
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1answer
197 views

SQL Server Index Scan Actual Executions

I have a fairly complicated query and running it on two databases with same schemas, but with different data produces different result. On database D1 the elapsed time is around 1 second, and the ...
0
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1answer
597 views

Query performance and join hints, plan cost, and duration

Having some trouble identifying why a query's duration would decrease when using OPTION (HASH JOIN) or OPTION (MERGE JOIN), although plan cost increases. Background I have a reporting database using ...
0
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0answers
21 views

How are RidJoins implemented in a database? [closed]

Please some one explain me how are RidJoins (Rowid Joins) implemented in the execution layer of the databases? What are the scenarios when RidJoin can give better performance?
0
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0answers
45 views

Eager Spool 100%

I have a query like below, when I execute it, the parallel query always takes very long time to finish, I found there is index spool(Eager Spool) which costs 100% in execution plan... How can I ...
0
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0answers
44 views

Why does this plan cost even though there are no rows?

I execute a Batch-Operation. The whole execution needs about 60s. The following statement needs 75.6% of the whole Batch-Operation: update WW_Pos set LieferantID=null where LieferantID in (select ...
0
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0answers
42 views

SQL query running slow compared to its earlier execution time

One of our application using an SQL query is reported running slow. Current execution time:- 15 minutes and so Earlier execution time:- 30 seconds. SQL-Sentry Plan for the slow query I've ...
0
votes
1answer
53 views

intermittent performance issue - query with multiple CTE and trashed execution plan

I'm trying to optimize a SQL query that shows variable performance (less than 2 to more than 15s). Overview This is a ColdFusion website, with a SQL Server 2008 R2 backend The query is part of the ...
0
votes
1answer
48 views

Optimizing a DMV query

I have found a query that is a major performance issue in my environment. I looked at the actual execution plan for this query and found out the main problem is the remote scan (98%). Its remote ...
0
votes
1answer
124 views

What are the OMem and 1Mem columns in the plan output?

The plan output, for example SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY_CURSOR( '' ,NULL,'ALLSTATS LAST')); has the columns OMem and 1Mem. What is their meaning? I could not find any reference or ...
0
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0answers
73 views

Index Tuning Question

I have the following query: SELECT T1.ITEMID, T1.ITEMTYPE, T1.PURCHMODEL, T1.HEIGHT, T1.WIDTH, T1.SALESMODEL, T1.COSTGROUPID, T1.REQGROUPID, T1.EPCMANAGER, ...
0
votes
1answer
83 views

same query different servers,different execution plan and time

I have this query and it runs less than 2 minutes on Test but on Prod it takes 10 minutes. Both are the same version,CPU,RAM,OS the same. I have four tempdb files on Prod but one one Test. I ...
0
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0answers
28 views

Analize Query in MySQL Server 5.1

I try use MySQL Workbench 6 to analyze the cost, but they don't show the cost of query. How i get this costs?