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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3
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1answer
214 views

Minimum rowcount for filtered index?

Creating an index always has trade-offs. Whenever you insert, update or delete, it has to perform those operations on the index as well. This is all pretty commonly known. But with the advent of ...
3
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1answer
281 views

Very large btree index with few rows (openstreetmap gis data)

I tried to import a subset of open street map data to a Postgres database using the standard tool (osm2pgsql). I then tried to rebuild the indices on the table using plain sql (dropping them, then ...
3
votes
1answer
4k views

Very slow simple PostgreSQL query on RDS

I seem to be getting very slow queries on a medium sized RDS box (db.m3.medium, 3.7gb ram). This is across a table of 4,152,928 rows.. select sum(some_field) c from pages where pages.some_id=123 and ...
3
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1answer
1k views

'ERROR: text search dictionary “unaccent” does not exist' during CREATE INDEX?

I'm running PostgreSQL 9.3 on Mac OS X Yosemite. I try to create an unaccent lowercase trigram index. To achieve it I did this: mydb=# CREATE EXTENSION pg_trgm SCHEMA public VERSION "1.1"; ...
3
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2answers
222 views

Why seq-scan can be much faster than index-scan and index-only-scan in this simple query?

I am using PostgreSQL 9.4.4. I have a query like this: SELECT COUNT(*) FROM A,B WHERE A.a = B.b a and b are the Primary Keys of tables A and B, so there are B-indexes on a & b By default, ...
3
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1answer
669 views

Drop primary key without dropping an index

Is it possible to drop primary key constraint on a table without dropping the index? I have a situation when I want to remove the PRIMARY KEY to get rid of the NOT NULL constraints and set it to ...
2
votes
1answer
126 views

what would be a good choice of clustered index (and other indexes) for this situation involving a indexed view?

To help me improve the performance of some queries I have created the following indexed view: CREATE VIEW DBO.vwOrders WITH SCHEMABINDING AS /*-------------------------------------------------------...
2
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2answers
88 views

How can one optimize a query involving a sort and a LIKE?

Here is the query: EXPLAIN ANALYZE SELECT * FROM "Users" AS "User" WHERE "User"."name" LIKE 'garr%' AND "User"."id" NOT IN (2449214) AND "User"."hellbanned" IS NULL AND "User"."...
2
votes
1answer
327 views

Index on column with data type citext not used

In PostgreSQL 9.4, with following schema: CREATE TABLE people ( id INTEGER PRIMARY KEY, name TEXT, junk CHAR(1000) ); INSERT INTO people(id, name) SELECT generate_series(1,100000), md5(...
2
votes
1answer
1k 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
4k 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 ...
2
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0answers
234 views

Finding missing_index_details in MySQL

MS SQL Server apparently can tell you what indexes would be useful for your query. Is there anything similar in MySQL? This article (scroll to "Find missing indexes") says that in Microsoft SQL ...
2
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3answers
298 views

Why does PK constraint require a separate index when I already have a suitable unique clustered index?

This is part of table definition from here: CREATE TABLE [dbo].[JobItems] ( [ItemId] UNIQUEIDENTIFIER NOT NULL, -- lots of other columns CONSTRAINT [PrimaryKey_GUID_HERE] PRIMARY KEY ...
2
votes
1answer
83 views

Do I need to reenter old data after adding an index to a table?

I want to add index to my tables. Some of my tables already have couple thousand rows. Do I need to reenter my stored data after adding index to columns (to make them aware of index/so the indexing ...
2
votes
1answer
419 views

Row with latest timestamp

How to get the row with the latest value in a TIMESTAMPZ column? Is an index needed? Does an index change the strategy? Would behavior vary by database (I'm using Postgres 9.4)? My app records data ...
2
votes
2answers
256 views

Is unique index better than unique constraint when an index with an operator class is required

Postgres docs say: The use of indexes to enforce unique constraints could be considered an implementation detail that should not be accessed directly. One should, however, be aware that there's ...
2
votes
1answer
65 views

Slow query on mid-size tables with good index coverage

I'm running a query that touches 2 moderately sized tables (1-5 million rows). EXPLAIN shows it touches only indexes and very few rows, however it takes very long to complete (~8 seconds). The only ...
2
votes
5answers
189 views

Lots of Indexes - MySQL vs MongoDB - Migrating

So, I've never used MongoDB, I just read a lot about it and I think it's going to be good for my project. Also, I do not have lots of experience with MySQL and to be even more honest I have no clue of ...
2
votes
2answers
247 views

Database events that will cause deletion of index

In SQL server if we try to change a data type of a column having index ,then it deletes the indexes associated with that column and changes the data type . I was not aware of it and was faced problem ...
2
votes
4answers
2k 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 ...
1
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0answers
198 views

Best practice for storing image order number in a database

I am designing a social networking website(mysql with InnoDB engine + php) where I need to store image sequence in a database. The table structure is as follows:- PicId (BIGINT, AUTO INCREMENT, PK) ...
1
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2answers
150 views

What to do with a table with too many indexes?

I'm the new DBA for this company. I'm seeing some of their tables have a LOT of indexes; for instance some have over 50 or 60. Is this a good thing? From my research, it seems this is not good for ...
1
vote
1answer
413 views

Should indexes automatically be placed into their own bufferpool?

We work with DB2 LUW (specifically we are currently on 9.7 FP4) running on AIX. Per best practices from IBM, they recommend that when you build a table, you place the data, the indexes, and LOBs/LONG ...
1
vote
1answer
93 views

Is an explicit KEY redundant if it is covered by a UNIQUE KEY?

I am auditing an application which I've been developing over the course of several weeks. I've noticed this in CREATE TABLE: UNIQUE KEY `baz_3` (`baz`,`foo`,`bar`), KEY `baz` (`baz`), Is the ...
1
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2answers
1k views

Mysql. Block/disconnect slow queries

I am experiencing issue. Someone 'attacked' my server: simply by searching the same phrase with multiple requests. As it is text search request and database indices are not used, the engine searches ...
1
vote
1answer
1k views

Slow insert with MySQL full-text index

I use a full-text index in a MySQL table, and each insert into this table takes about 3 seconds. It seems that MySQL rebuilds (a part) of the full text index after each insert/update. Is this right? ...
1
vote
2answers
207 views

Should I create an index for non key columns?

I have a table in a PostGreSql database defined as following: CREATE TABLE public."MATCH"( "ITEM_A_ID" bigint DEFAULT 0, "ITEM_B_ID" bigint DEFAULT 0, "OWNER_A_ID" bigint DEFAULT 0, "...
1
vote
2answers
259 views

Mysql might have too many indexes

I am using the php framework Laravel for my application, together with mysql 5.6, in order to have full-text search with innoBD. But I am not sure if I have too many indexes. My application allows ...
1
vote
0answers
917 views

Based on these DBCC SHOWCONTIG stats, should I index this table?

I have a SQL 2008 Standard server on full mirror (safety). I reorganize all indexes weekly. I am looking into rebuilding a few indexes to improve performance. I ran DBCC SHOWCONTIG on my largest, most ...
1
vote
1answer
782 views

Change a partitioned global non-unique index that is the primary key to a non-partitioned unique index

One of the largest tables in our system has its primary key setup as a globally ranged partitioned (in huge, useless, multi-billion value ranges) non-unique index. Its values are just a sequence ...
1
vote
1answer
3k views

Varchar index - will hashing value make it faster?

I have a VARCHAR(1000) column in a table. It will contain strings that will not be guaranteed to be unique. I have a query that searches this column as part of a WHERE IN clause, the list of values in ...
1
vote
1answer
71 views

Multi-Column PK or Auto-Increment PK?

In another question I mentioned that I have a table where, in order to ensure uniqueness, I need to use multiple columns as the PK. However, lookups are usually only done using the first of those ...
1
vote
2answers
418 views

Estimation of creating index in SQL Server

We create new index on our production database, with a few fields, our database size is around 300GB and it works for one hour and do not finished yet. How can you estimate this operation? If we ...
1
vote
1answer
103 views

Low cardinality fields: integer or string

A Ticket has the statuses: new in_progress on_hold closed I could make ticket.status a string (on_hold) or an unique int(2). It is indexed. Int pros: smallest size in index Int con: low clarity ...
1
vote
1answer
196 views

Optimizing Postgres query

I've got a one to one relation from users to addresses table. Where one user can have one search address and one verified address. I've got two indexes on addresses table : Index on state field ...
1
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2answers
387 views

Find missing indexes

tool available to find missing indexes in mssql 2008 ? can we find the missing index using Database Engine Tuning Advisor
0
votes
2answers
1k views

How to index for a query with independent range conditions?

What is the best way to index a table that I query using independent range conditions? E.g. WHERE X < ? and Y > ?
0
votes
0answers
25 views

MySQL JOIN is fast, but selecting column is slow

My logs table has half a million rows. Each row has an indexed log_level_id column pointing to table log_levels (with only 5 rows). On log_levels, id is an auto-increment primary key and label has ...
0
votes
1answer
70 views

query not taking index into account

EXPLAIN EXTENDED SELECT SQL_CALC_FOUND_ROWS SQL_NO_CACHE g.*, u.user_id FROM geotable g JOIN userstable u ON g.uid = u.uid -- corners selection: WHERE (lat BETWEEN ? and ? AND lon ...
0
votes
1answer
32 views

Necessary to have separate index for lookups against one of a multi-column PK?

Sorry if this is a FAQ, but I'm having problems turning up exactly what I'm asking: I have a table (mysql) with a primary key which is composed of multiple columns only because this is necessary to ...
0
votes
1answer
394 views

Is ANALYZE useful immediately after creating an InnoDB index?

Let's create a new index on an existing table: CREATE INDEX `IDX_some_index` ON `some_table` (`a_column`, `another_column`); Is this useful? ANALYZE TABLE `some_table`; Can anyone point to ...
0
votes
1answer
58 views

Postgresql error: failed to re-find parent key in index

I haven't seen this before and am stumped. I have a Django app with a postgresql 9.3 DB (hosted on Ubuntu VM), and very recently I VM ran out of disk space (resulting in no space left on device ...
0
votes
1answer
320 views

Increase performance WITHOUT adding indexes [closed]

I'm having a rather large table (350MB, 1.3M rows) and there are dozens of queries arriving at this table every second. Most queries are super-fast thanks to indexes - but some others aren't. ...