A database structure that can improve the speed of queries at the cost of disk space and slower inserts/updates. It stores a copy of one or more columns but structures the data differently to allow for faster access.

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How to partition an Oracle table with 65 million rows?

The table that needs partitioning contains a list of Components and their Values. So one table is tblComponents. Another is tblFields. Then this table, tblValues, contains the values of the ...
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4answers
333 views

how to explain indexes

This question is about teaching: When I learned databases, we talked about indexes being like the card catalog in the town library. We had at least an author index, a title index, then the Dewey ...
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1answer
916 views

Index for speeding up sorting by boolean, timestamp

For a website that displays recent news, I have this query on the home page: SELECT * FROM "cms_news" WHERE NOT ("cms_news"."timestamp" >= '2013-08-08 13:32:39.778988+00:00') AND ...
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0answers
239 views

Fulltext search returning too many rows

Server: MySQL 5.1.66-0+squeeze1 My problem: I have two databases with the same tables. One is for the testing environment and one for production. When I perform a MATCH AGAINST on the prodution ...
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1answer
202 views

In MySQL if column X has unique values what's the difference between UNIQUE index and B-Tree index

Let's assume that I have table data: CREATE TABLE `test`.`data` ( `row_id` INT NOT NULL , `data_id` INT NOT NULL , PRIMARY KEY (`row_id`) ); Now, let's assume that data_id has unique values. Is ...
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2answers
8k views

Index for date column for range query in Oracle?

We have a lot: select count(*) from TBL where XDATE between ? and ? and FLD = ?; We expect to boost performance by tuning index on XDATE column (which have DATE type). What type of indexes more ...
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2answers
232 views

Full text catalog does not allow me to hit on singular forms

I have created a full text catalog for a column under database name -> "Storage" -> Full Text Catalogs. It is accent sensitive and "default catalog" is set to false. The language for the column ...
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0answers
363 views

PostgreSQL index array of int4range using GIN / GIST - custom operator class

Here is my table: CREATE TABLE mytable ( id INT NOT NULL PRIMARY KEY, val int4range[] ); I want to index the val column: CREATE ...
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1answer
80 views

What indexes to add on MySQL table

I've been trying to optimize my table, but am yet unable to get the desired results. CREATE TABLE IF NOT EXISTS `puzzles` ( `puzzleID` int(7) NOT NULL, `puzzleMask` varchar(30) CHARACTER SET utf8 ...
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2answers
335 views

Adding an index to a system catalog in Postgres

I'm having a situation very similar to the one described here: I've got a SaaS situation where I'm using 1000+ schemas in a single database (each schema contains the same tables, just different ...
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2answers
1k views

MySQL Cluster - Table is full [Error 1114] while still creating tables

I am trying to forward engineer a MySQL Workbench model with about 100 tables to a development single-node cluster and, while creating the 51th table, I end up getting a "1114 table is full" error, ...
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2answers
686 views

Avoiding a sort on an already clustered index for group by

On a table T with two fields, pid and did, the following query results in a seq. scan followed by a sort on pid: select count(did), pid from T group by pid Here is the query plan: ...
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2answers
4k views

LIKE uses index, CHARINDEX does not?

This question is related to my old question. The below query was taking 10 to 15 seconds to execute: SELECT [customer].[Customer name],[customer].[Sl_No],[customer].[Id] FROM [company].dbo.[customer] ...
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1answer
2k views

Query taking non-consistent time to execute [closed]

I have a query which takes large time to execute sometimes.When i checked the speed it was taking 15 seconds.But actually it should run faster than that.When i again checked the query it again ...
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2answers
756 views

Question about non-clustered index storage in SQL Server

I have a table people with two non-clustered indexes. create table people( id_person int, first_name varchar(50), last_name varchar(50), city varchar(100), state char(2), zip_code int ) CREATE ...
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1answer
181 views

Index method for very few updates and many inserts

I am using Postgresql 9.1 with *pg_trgm* extension. I need to create an index on a text-based field. I do not need full-text searches, I use ILIKE queries to make my searches. I will use pg_trgm but ...
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2answers
2k views

Should I refresh query plan cache

Please let me explain my problem and situation: I have a web application - MVC3, MSSQL Server 2005, LinqToSQL. It has been running great until one fine morning I pushed a lot of rows to a table that ...
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2answers
104 views

Using an index for both uniqueness and fast lookup?

Right now I have a postgresql 8.4 database set up for players in a multiplayer game. I want the username column to be unique. I also want to be able to lookup a player by username quickly. Here's the ...
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1answer
13k views

CREATE INDEX vs ALTER TABLE ADD INDEX - MySQLism, or SQL Standard?

Just came across a weird issue, whereby depending on how I create an index, an index name is required. http://dev.mysql.com/doc/refman/5.5/en/create-index.html ...
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2answers
5k views

How to choose a collation for international database?

I'm designing a database which will store data in different languages (using UTF-8), so I think the best way to display the queries results is ordering it according to the user's language during the ...
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1answer
373 views

optimizing MySQL for traffic analytics system

background : I've developed a URL shortener system like Bitly with same features , so the system also tracks clickers info and represent as graphs to the person who has shorten the link as ...
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1answer
409 views

How can a fill factor of 0 or 100 be the same?

As of my understanding, Fill factor of 80 implies that 20 percentage of each leaf-level page will be empty to enable future growth. I can't correlate how fill factor of 0 and 100 can be the same! Am I ...
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4answers
797 views

When do I use another type index than integer? (eg string) [integer vs string index]

I was reading about relational databases like sqlite and I always see the schema for user storage like: UserID (index) | Username | Password but wouldn't it be actually much faster to use Username ...
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1answer
826 views

Would adding indexes to my foreign keys improve performance on this MySQL query?

Consider the following query: SELECT `locations`.`id` AS `location_id`, `locations`.`address`, `locations`.`lat`, `locations`.`lng`, `tickets`.`status_id`, `customers`.`name`, ...
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1answer
78 views

Indexes and Optimizations for Logging System

I'm designing tables for a new log system and am having trouble figuring out what indexes I'll need (I'm a developer, not a DBA), and am also open to any suggestions/criticisms/etc. for making the ...
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1answer
928 views

Partitioning vs Indexes

I'm very new to databases, so I apologize if my question is very basic... Anyways, I'm creating a table with what seems like alot of data (500 million rows right now, and potentially twice as much in ...
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3answers
688 views

index mysql concatenated columns

I have a table for author names with two fields, first_name & last_name, both varchar(55), both nullable (for crazy business logic reasons) although in reality last_name is unlikely to ever be ...
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3answers
1k views

Meaning of “nonclustered located on primary”

When I run sp_help (using ALT+F1) for a table, on the indexes, there is a column index_description. and the rows have for example: nonclustered located on PRIMARY (on foreign keys) nonclustered, ...
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3answers
238 views

Unused Indexes - Consider Primary Key Constraint Supporting Indexes?

I have given a task to find out the unused indexes in my production environment. I'm using a DMV to find the unused indexes should i include the Primary key Clustered Indexes on it? If a Primary key ...
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1answer
376 views

Postgresql table with one integer column, sorted index, with duplicate primary key

I want to have a table in PostgreSQL with these properties: One column with an integer Allow duplicates in this column. Duplicates will be rare. Duplicates have no meaning logically and will be ...
4
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1answer
111 views

What is the difference between these two index declarations and do I need both?

I was examining a script with 'Display Estimated Execution Plan' and it made several recommendations for indexes to add to the database. I added them and the script did indeed run much faster. Now ...
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3answers
3k views

Nonclustered index is faster than clustered index?

Both tables have same structure and 19972 rows in each table. for practicing indexing, i created both tables having same structure and created clustered index on persontb(BusinessEntityID) and ...
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682 views

Index usage stats DMV indicates no index activity

I'm trying to obtain information on indexes. According to several websites, the below TSQL query should join information on indexes to the indexes table, returning indexes and related information. ...
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1k views

Update performance: clustered versus covering index

I have a simple, 3-column table with about 50 million rows in it. This table gets about 5,000 inserts/updates per second, and perhaps 20 queries per second are executed against the table. The table ...
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5answers
4k views

What happens when we create index

What happens exactly when I create an index on the empid column of this employee table CREATE TABLE employee ( empid number(5), ename varchar2(30), sal number(10,2) ); Let's assume the ...
2
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1answer
591 views

Does the size of the primary key contribute to table size?

I have a table (InnoDB) with data length around 36G and index length 23G. It had a composite primary key across three columns. As an initial attempt to reduce the size of this table, I dropped the ...
2
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1answer
476 views

Why does selecting top 1 from composite index DESC also used to partition by month not select the top value?

We have very large database table that I need to select the value of the max id. Given the table size SELECT MAX(id) FROM tableA will not perform well enough. Table definition (with columns omitted ...
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0answers
71 views

How to/advice for hosting a multi-user database on the cloud with specific objectives

I have developed an application that users will be able to download and create an account with through our company. This application will always be connected to the internet. I have been testing the ...
2
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1answer
391 views

Rebuild an index while it is being referenced in Oracle

I have come across many articles on this site and on Tom Kyte's blog on the how, whys and whens of Re-building indexes. Note that this question is about whether I can rebuild when there are concurrent ...
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1answer
185 views

Updating an FTS indexed column returns “Invalid InnoDB FTS Doc ID”

Environment: Ubuntu 12.04 (and 13.04) MySQL 5.6.11 I have a table which has a full text index on it (real table has much more columns and rows): DROP TABLE IF EXISTS articles; CREATE TABLE ...
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2answers
339 views

If I update a column record in a table, will indexes that do NOT have this column in it be affected?

In terms of performance if I have a table like so: CREATE TABLE [TESTDATA].[TableA]( [Col1] [nchar](5) NOT NULL, [Col2] [nchar](2) NULL, [Col3] [float] NULL CONSTRAINT [TableA_PK] PRIMARY ...
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2answers
180 views

Indexing strategy for dynamic predicate

Assume SQL Server 2012 Standard edition. My database has a table with 500 million rows. The table has about a dozen columns, none of which are very wide (some varchar(100)'s and some ints). The ...
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1answer
760 views

Index on foreign key makes query extremely slow

We are recently experiencing a tremendous query slowdown with spilled over temp tablespace. A specific query causes this problem. The queried table (table3) has an indexed PK, three FK with indexes ...
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6answers
2k views

Why don't databases create their own indexes automatically?

I would have thought that databases would know enough about what they encounter often and be able to respond to the demands they're placed under that they could decide to add indexes to highly ...
0
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1answer
53 views

MYSQL - Using simple inventory number convention as Primary Key

I have an inventory with three numbered groups like so: Group 1: 0-999 Group 2: e0-e999 Group 3: v0-v999 Can I simply make a one-column table to store this information and make that column the ...
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4answers
793 views

MySql Order by isnull() Performance Problem

my sql below is use for listing stock added from 10 days ago. Order by isnull(Price) is use so that stock without any price yet will still being listed. AddDate and Price has an index. SELECT Id, ...
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420 views

Run query faster, what index to use

I have a table with 85M rows : CREATE TABLE emissions_totales ( "schema_source" varchar(150), "snap" varchar(20), "gid" varchar(255), "polluant" varchar(50), "emi" float8, "numreg" varchar(3), ...
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1answer
989 views

How to set SQL Server index pages per fragment?

I have SQL Server 2008, and a number of databases. I have discovered that one of my table's indexes is extremely fragmented (How I know: http://msdn.microsoft.com/en-us/library/ms189858.aspx) The ...
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0answers
157 views

How implement MySQL unique index with two foreign key that one can be null?

I would know if can be declared in MySQl to create an index constraints in a table with two foreign key that one can be null. For example cannot be repeated a null foreign key with the other foreign ...
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1answer
334 views

Is index on foreign key used? (No difference in EXPLAIN.)

Essentially, I am joining two MyISAM tables and have found that the EXPLAIN output for the query does not change regardless of whether I have an index on the foreign key in the parent table. I'm not ...