The process of determining which indexes are useful and which are not.

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725 views

MySQL: logging queries which would execute without using indexes

I am trying to use log_queries_not_using_indexes = 1 to find queries which are not executing optimally on a MySQL server. However, I find the resulting log file of rather limited value. Apparently, ...
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183 views

How to count selectivity rows in PostgreSQL 8.2

I have problem with two queries on PostgreSQL v8.2. It seem like the optimizer chooses a wrong index: db=# explain select count(*), messagetype, alias from event where templateinfoid = 10 and ...
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38 views

Can I rely on the order of colums on an index generated by Database tuning advisor

I got the following recommendation on a table: CREATE NONCLUSTERED INDEX ...
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1answer
1k views

What are the disadvantages if indexes are added on all columns?

I know, that it is not a good design to set too many indexes, but just for understanding the theory: What exactly are the disadvantages if you add an index on all columns in a table in MySQL? Are ...
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2answers
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Indexing is not working

Following is the table and index information for which I have the queries at the end. Create Table: CREATE TABLE `food` ( `id` int(10) unsigned NOT NULL DEFAULT '0', `page_no` int(11) DEFAULT ...
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1answer
139 views

How can I determine what is using a particular resource (table, view, or function, etc) on my SQL Server?

I've been looking for tables that could use better indexing. I've created a stored procedure that provides a list of tables that have no indexes other than a primary key: CREATE PROCEDURE ...
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1answer
419 views

Best practice around sys.dm_db_missing_index_group_stats in SQL Server

I have a fairly simple query using sys.dm_db_missing_index_group_stats that identifies missing indexes in my SQL Server database. This is pretty commonly used. My question is how do I identify which ...
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1answer
154 views

After Rackspace server creation, PostgreSQL query planner doesn't work as expected

We created an image of one of our database servers in Rackspace. Then, we created a new server using that image, expecting things to work. However, the index performance we have seen seems to be ...
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667 views

Is Reorganizing Indexes required after ShrinkDatabase or can I just reogranize index with fragmentation more than 10%?

I am a new DBA to a SQL 2005 production Report server. My predecessor created a Maintenance Plan with 4 tasks: CHECKDB; SHRINKDATABASE (N'DB1',10,TRUNCATEONLY); it seems to be running a REORGANIZE on ...
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592 views

Finding stored procedures with missing indexes

How to scan for stored proc that need indexes to be created. Anyone have any idea? Basically we have stored procedures that run very slowly. I'm wondering if there is some kind of automated script ...
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1answer
494 views

Optimizing an audit table for inserts and deletes

I'm trying to identify the best way to design a table for audit purposes. Basically I log several last events for many users in one table. There's a limit on the number of records for each user. The ...
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1answer
163 views

Is there any reason to use index for very small tables (up to 1000 rows)?

During application development I have a lot of tables that store "small" amount of data (usually 10-40 values, id + value and sometimes type) which hold attributes for "objects", like fresh/rotten, ...
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62 views

How can one improve the performance of a query that selects on a low cardinality column in MySQL?

I have a "State" column that has a low cardinality (three possible value), on which most of my queries perform an equality selection (WHERE col = 'blah') AFAIK you need something like a bitmap index ...
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1answer
78 views

Index Evaluation

I have been doing some index evalaution on a table and this is the first time I have ever looked at how well indexes are performing so and would like some advice on a certain index. The non ...
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1answer
87 views

What is a suitable index for this query?

Below query is taking long time - around 540 seconds. The table did not have any indexes. I created indexes on columns in the WHERE clause and other fields but the query is not using these indexes. ...
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519 views

What am I doing wrong with the Database Tuning Advisor?

My background: I'm a dev/architect, not a DBA. Sorry! So we have a ~400 table 75GB database. I ran Profiler for ~24 hours ("Tuning" template minus LoginName) and have ~7GB of usage recorded in a ...
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55 views

MySql include partition key in index?

Please look at the following Mysql table: http://pastebin.com/b0NDSbdz I've partitioned the table by sent_at and I'm making sure that most of the queries pass sent_at. do I need to include sent_at in ...
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292 views

Query Performance Tuning on a huge table

I have the following table Transactions. The table looks like this: CREATE TABLE [dbo].[Transactions]( [TransactionID] [bigint] IDENTITY(1,10) NOT NULL, [PlayerID] [bigint] NOT NULL, ...
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392 views

Use GIN to index bit strings

I'm trying to extend PostgreSQL to index bit strings up to 1000 bits. (These bit strings are created by quantization of high-dimensional vectors, so for each dimension up to 4 bits are assigned). ...
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2answers
1k views

Multicolumn index and performance

I have a table with a multicolumn index, and I have doubts about the proper sorting of the indexes to get the maximum performance on the queries. The scenario: PostgreSQL 8.4, table with about 1MM ...
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1answer
483 views

Which stored procedures are using a specifc index

I've been reviewing the indexes in our databases (adding missing indexes and removing bad ones). I stumbled on an index I created months ago which looks way to good to be true. Since the last server ...
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1answer
165 views

What would be a optimal index for this query in mysql

I'm trying to optimize this query. SELECT * FROM sales_reps WHERE account_id = 1 AND (state = 'enabled') AND (clients >= 5 OR revenue >= 10000) ORDER BY name, platform, client_group, ...
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1answer
122 views

Performance impact of including result column in indexed columns

I have a database (in MySQL, using InnoDB) that I am using for texture identification in a 3D image. In it, there will be a table of texels(texture pixels) with hue included, in the form of: texelid ...
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108 views

Optimizing index creation

One thing that has bothered me for awhile is creating many many indexes for the one table where the query only differs slightly or contains many of the same columns. An example case would be: table1 ...
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134 views

How to optimize this query?

Query: Select * from `t_event` where `create_user_id`=7 and (`event_create_date`)=('2012-12-18 00:00:00') and `event_type_cd`=11 and `domain_id` =602 and `job_id` =1 limit 1 Table structure: ...
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229 views

Simplify and optimize a complex query

Our site has a chronological event feed that uses MySQL. We have noticed that some of the queries tend to run for quite a bit longer than others. For example, some queries for our heaviest users take ...
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674 views

Cardinality rule for bitmap indexes

The Oracle documentation includes the following advice: A bitmap index should be built on each of the foreign key columns of the fact table or tables In that reference, there is even a bitmap ...
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1k views

Best way to organize compound indexes on partitioned table (date by range)?

I have a table with an auto increment primary key, but in order to use the partition feature in MySQL I had to include the date in the primary key so I would use partition by range using the date ...
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3answers
159 views

Determining if indexes are redundant

I have a table with the following structure: Id (int identity PK) FooId (int FK) BarId (int FK) QuxId (int FK) Other fields The following indexes have been defined: PK (Id), clustered Index1 ...
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1answer
309 views

Is staggering reindexing jobs a good strategy?

I have inherited a server with 35 databases and a job that reindexes all tables on all databases (using sp_MSForEachTable). It's taking over 14 hours to complete and is now blocking other processes. ...
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1answer
486 views

SQL Server 2008 Maintenance Plan Failure

Instead of using my old school index rebuild script I had decided to use 2008's built-in Maintenance Plan to do a simple Rebuild Index task. The details are: Connection = Local server connection ...
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2answers
131 views

index maintenance strategy if few insertion points relative to # of rows

In SQL Server 2008 R2, I have a nonclustered covering index on multiple tables with 100M+ rows. The table has a few thousand "insertion points" where all new inserts happen. This means that regardless ...
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327 views

Can indexing views in SQL Server 2005+ speed up SELECT count(*) from a View?

My initial question was How does someone determine if it is a good idea to index a view?. Update: My underlying assumption was that indexing views speeds them up. This is apparently not sensible, ...
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62 views

Is it any potential problem with having 2 constraints suppored by one index in Oracle?

I have the following table : CREATE TABLE action (action_id INT NOT NULL, action_type_id INT NOT NULL, action_date DATE NOT NULL); CREATE INDEX IDX_ACTION_ACT_TYPE_ACT ON action(action_id, ...
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2k views

How I should fix the following update statement to make it run faster?

I have the following DML: UPDATE rc_usutb011 u SET cod_ant=( SELECT cod_hst FROM rc_pdptb101 p WHERE ocip_hst=ocip_ant AND p.sector=u.sector ); The explain plan ...
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3answers
162 views

What is a good guideline for sampling for statistics updates

Scope: A billion record table that is indexed in 10 ways. Rate of change per day is 1/2 a percent. Some of the indexes are monotonously increasing (datetime/timestamp), yet the common queries most ...
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659 views

Filtering data ordered by rowversion

I have a SQL table of data with the following structure : CREATE TABLE Data( Id uniqueidentifier NOT NULL, Date datetime NOT NULL, Value decimal(20, 10) NULL, RV timestamp NOT NULL, ...
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1answer
903 views

What factors go into an Indexed View's Clustered Index being selected?

Breifly What factors go into they query optimizer's selection of an indexed view's index? For me, indexed views seem to defy what I understand about how the Optimizer picks indexes. I've seen this ...
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1answer
108 views

Does updating a partially indexed field add or remove it from an index in Postgres

We can create a partial index for a field in Postgres. I am looking at using this to stop rows which are archived from being in an index on a created_at field: First we create the index: test=# ...
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1k views

Viable strategies for rebuilding indexes online in SQL Server 2008 R2 Standard edition?

We use SQL Server 2008 R2 Standard edition (we can't afford Enterprise edition on all our production database servers) and have to periodically maintain the critical indexes (rebuilding/reorganizing) ...
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484 views

SQL Server Database Engine Tuning Advisor vs DMV queries

What is the best way to tune the indexes on my production database? I normally use the following query : SELECT user_seeks * avg_total_user_cost * (avg_user_impact * 0.01) AS [index_advantage], ...
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3answers
893 views

Lookup table for a one-to-many relationship

I have a tickets table with an id that I need to associate to a lookup table where the counterpart of that data is another id that is controlled from an outside source. tickets - id - sutff lookup - ...
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1answer
93 views

What is the best relationship model for high performance?

I want to model a relationship between Customer and Transaction. However, because Customer is only described by a unique string and no extra info, I have two possibilities to implement it in the ...
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1answer
289 views

Analyzing TCB Index Status for DB2

The Following is the TCB index that I could get using a command for my DB2 database. I don't know how to analyze it. Which columns are important? What do they mean? TCB Index Stats: Address ...
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1answer
179 views

INDEX Creation Advice Oracle

I have a table that has time data of 2 billion records obtained from the clients. The data has two main columns, date and entity_id. The attributes date, and entity_id would make a unique pair. ...
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2answers
2k views

How can I improve the speed of a query on a 20 million+ row table?

I have a query that is used for getting internet traffic statistics of certain IP addresses. There are separate IP address fields for hosts and blocks of IPs called assignments. The data is stored ...
2
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1answer
214 views

Oracle function based index is not used in query

I cannot figure out why the following is not working as I expect it : CREATE TABLE table1(table1_id INT NOT NULL PRIMARY KEY, col1 INT NOT NULL, val1 VARCHAR(50)); CREATE INDEX ...
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332 views

Using indexes to create multiple relationships to a table in order to enforce data integrity and add meaning

I'm working on an inventory database that uses supertype/subtype model. My question regards creating multiple relationships with the same tables using the primary key and composite indexes that also ...
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1answer
118 views

Where to place non clustered index

Execution plan clearly showing that one of my table used in query is useing Clustered Index Scan. From this node, how can i guess that which columns should be part of my non clustered index key and ...
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2answers
462 views

Reorganize Indexes T-SQL

I'm moving a database to SQL Azure and with that I lose the maintenance plans so I am going to use a Worker Role to schedule them. When I open the properties of the Rebuild Index Task and click on ...