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

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1answer
430 views

Is there any way to save the execution plan in a file in PostgreSQL?

By saving a plan in a file, I don't mean to view it, but force the optimizer to use the saved plan to execute some query. For example, if the optimizer chooses to do a hash join for a two-table ...
2
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2answers
863 views

Why is query using Clustered Index when it shouldn't?

Let us presume I have a table named Category in a SQL Server 2005 database. Category has category_id (bigint, identity) as its primary key and name (nvarchar(50)). There is obviously a clustered ...
2
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1answer
336 views

Postgres planer JOIN removal

I have two tables, one contains a lot of rarely update data, and one contains a little of frequently update data. Every record in second table has corresponding record in the first, like following: ...
2
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2answers
99 views

Execution plan has TOP operator for query without TOP or ORDER BY

I have product sales by month temporary table.(subset of much larger historical table) I'm running query to find new product not previously sold in the previous months for a specified 6 month range. ...
2
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1answer
120 views

Same query sometimes uses a Table Spool

I'm checking out a query which exhibits strangely inconsistent performance. Using SolarWinds DPA, I can see that the query sometimes uses a Table Spool, sometimes it doesn't. When it actually used a ...
2
votes
1answer
2k views

Fast paginated result, for various filter clauses

I have been working on obtaining a paginated result from a table in my database (11g). While I have a query that does work (ie, the result is correct) it does not perform as well as I'd like to and I ...
2
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3answers
5k views

Revert to old plan in Oracle

A weekly, scheduled, schema wide stats update was run on our Oracle 11R2 RAC cluster on Sunday. One of the queries had no apparent data or code change but now runs at 3 hours instead of 20 minutes. ...
2
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2answers
1k views

In DB2, how can I disable NLJOIN?

I want to indicate to the optimizer, via SET or optimization profiles, that NLJOIN shouldn't be used at all when optimizing a query. I've been looking for this for a while without any success. I ...
2
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1answer
25 views

Turn off auto qualification of table names when creating a view

Problem Definition I am trying to modified a shared development database, for a dev team to use for application development/testing. Most of the collective work (table names, views, etc) are stored ...
2
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1answer
42 views

Oracle and execution plans

I have used the following procedure to view the last execution plan create or replace procedure display_plan as begin for c in (select plan_table_output t from table(dbms_xplan.display_cursor('', ...
2
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3answers
82 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?
2
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1answer
461 views

Keep Execution Plan in Cache - SQL Server 2012

How can I keep a query execution plan in SQL Server's cache and use it several times? When I execute a query for the first time it takes 7 seconds. After that it takes only 1 second. This query is ...
2
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1answer
44 views

Does DBCC TRACEON() invalidate cached execution plans?

In Microsoft SQL Server, does DBCC TRACEON() invalidate cached execution plans, same as SP_Configure invalidates all stored procedure plans ?
2
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1answer
436 views

Monitoring the Postgres query parser

As I understand it, when you send a query to Postgres like: SELECT id FROM table1 WHERE name = $1; Postgres will create a query plan. The plan will be cached for the same query in the same ...
2
votes
1answer
81 views

Understanding the simple execution plan in PostgreSQL

I'm new to execution plans still trying to learn. My problem is for below query select * from item limit 3; I got following execution plan, "Limit (cost=0.00..0.07 rows=3 width=75)" ...
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2answers
2k views

Estimated vs Actual Number of Rows

I have 5 tables that contain data split by quarter each table has a similar structure to the following: ID_Column bigint PK, EventType int, DateStamp datetime PK CustomerId int, ARG_1 nvarchar(32), ...
2
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1answer
605 views

Non-clustered Index Update not displayed in execution plan [duplicate]

Possible Duplicate: Nonclustered Index Insert I'm trying to work out the cost of having a nonclustered index on a particular table, but I don't see any maintenance cost in the execution ...
2
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1answer
271 views

Query tuning - SQL Server

One of our developers are trying to run the below query on a development server, which involves pulling data from a linked server, production. The query ran for more than 14 hours before it was ...
2
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2answers
522 views

Clustered monotonically increased index insert performance

I have a table with field Id (bigint, IDENTITY) as primary key and clustered index on it. I inserted 400 rows and saw execution plan. I got: the relative query cost for this insertion 36% and for this ...
2
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1answer
146 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 ...
2
votes
1answer
126 views

Why is my composite index not used for this table?

I am working with a fairly complicated schema, but I've simplified it for the purposes of this question. Table "public.scheduler_appointment" Column | Type ...
2
votes
1answer
398 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
62 views

Performance differs on same query against two (almost) identical tables?

I'm running these two queries in SQL Server 2012: SELECT tpua.Field1, CAST(round(twg.Field2 * 2, 0) / 2 As Decimal(8,1)) As Field2, CAST((round((twg.Field3/10.0) * 2, 0) / 2) * 10 As int) As ...
2
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0answers
86 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
170 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
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0answers
83 views

When will SQL Server automatically use a supporting indexed view?

I have the following expensive query that runs against our data warehouse: SELECT d.DateYear, COUNT_BIG(*) AS WidgetCount FROM Widgets AS w JOIN Dates AS d ON d.DateId = w.DateId WHERE ...
2
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1answer
200 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
210 views

Does Oracle ADO.NET varchar parameter size influence query plan reuse?

I am considering to apply a fix which will generate constant parameter sizes for (n)varchar parameters. The application is based on NHibernate with the old OracleClientDriver (using Microsoft Oracle ...
2
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0answers
146 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
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0answers
233 views

Postgres - Partitioning old tables, partition query planning, optimisation

I've been trying to optimise our database, but not being a DBA and not having done a whole lot of tuning before I'm struggling a little with "too many options". I've already run pg_tune and bumped a ...
2
votes
1answer
563 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 ...
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2answers
60 views

Understanding Execution Plan

I am really having hard time understanding the below execution plan. Query 1: (Simple Select Query) Record count of ##SALES_UNIT_RESULT is 168. In first execution plan it is fine. ;WITH ...
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1answer
211 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 ...
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2answers
3k 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
vote
1answer
133 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
65 views

Why does the query plan still sort a table despite having an index sorted on the columns?

I'm using Postgres 9.1 I have two tables I am joining: wikidb=> \d page Table "public.page" Column | Type | Modifiers ...
1
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1answer
104 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 ...
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1answer
139 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], ...
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2answers
71 views

deteriorating stored procedure running times

I have a stored procedure that is executed by my web application. Today, when an end user started an operation that affected more rows than usual, I started getting calls that the wait times for the ...
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1answer
207 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 ...
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1answer
44 views

SQL Server execution plan is using PK instead of index

The following query is taking 5 seconds to return 9692 rows: SELECT Project.CalculateSequencialProject, Project.CreateDate, Project.OpeningDate, Project.ForecastClosingDate, ...
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1answer
111 views

mysql query choosing an incorrect execution plan

I have a primary with an dependant subquery as a where condition that is choosing a wrong execution plan, and therefore is running for ever. Main query: SELECT rtr.id AS id156_, ...
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1answer
69 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 ...
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vote
1answer
74 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 ...
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1answer
3k views

Have Postgresql query planner use nested loop w/ indices over hash join

I'm having a problem with some StackOverflow-schema related data loaded into PostgreSQL 9.3.4. I have a query that is taking about 10x longer than it should, due to the fact that it is choosing to use ...
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vote
1answer
201 views

Algorithm used to perform offset/limit over a union all result set

I have two result sets: rs1: id name serial text ________________ 1 Nick .................... 1233112 Pete rs2: id name serial text ...
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1answer
886 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 ...
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2answers
203 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 ...
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2answers
2k views

Improve performance with the WHERE NOT IN sub-select clause

In the following query, I have to count transactions for each customer. [EDIT]However, I have to exclude from the result set entirely, customers that have a transaction older than one year. ...