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
788 views

Error when creating an index in SQL Server 2012

I'm trying to create the following index on our test environment (SQL Server 2012): CREATE NONCLUSTERED INDEX [iTransaction-OriginatingTransaction] ON [dbo].[Transaction] ( ...
3
votes
1answer
212 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 ...
2
votes
3answers
277 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
171 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
84 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 ...
2
votes
1answer
60 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
2answers
180 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
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 ...
2
votes
1answer
3k 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
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
votes
1answer
79 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
2answers
1k views

IN Clause causes Execution plan to change from Nested Loops to Hash Match

I'm tuning a query and have discovered some behaviour I'm not clear about. If I remove the WHERE IN clause the query runs in 3 seconds instead of 3 minutes. There only 7 rows returned in the ...
1
vote
2answers
69 views

Partitioned Tables and Indexes - what are the downsides?

When talking about Partitioned Tables and Indexes for tables with less than 100 partitions, no nonaligned indexes: with that I mean: Nonaligned index An index partitioned ...
1
vote
1answer
68 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
0answers
66 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 ...
1
vote
2answers
204 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
1answer
108 views

Index optimization on a view using a full outer join

Table structure: Foo FooChild Bar --- -------- --- ID ID ID Date FooID Date ...
1
vote
1answer
121 views

Is database record access sequential after retrieving the indexed page from disk? [closed]

This question was posted on Stack Overflow but left unanswered, I was hoping maybe here I might find an answer. What I understand about databases that if a queried or requested record is found in the ...
1
vote
0answers
163 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
vote
2answers
158 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
1answer
174 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
vote
0answers
777 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
91 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
vote
1answer
2k 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
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
655 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
923 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
1answer
365 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 ...
0
votes
0answers
45 views

Is it a good idea to disable lock escalation while adding new calculated columns to a table?

Having in mind that I can add computed columns to the subscription tables according to this link: SQL Server : Transactional Replication Computed Column Is it a good idea to disable lock escalation ...
0
votes
1answer
31 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
213 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. ...
0
votes
1answer
335 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
68 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
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 > ?
-1
votes
4answers
425 views

Index on 'GROUP BY' with functions

I have a log table. It logs visitor data (time of visit, browser, window size ...). I want to create reports. I use a query like this (MySQL): SELECT COUNT(*) as raw_views ... FROM logs WHERE ...