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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2answers
35 views

Compressing partition - what about index?

To save space on disk I want to compress some partitions of my tables: alter table TEST_TAB move partition TEST_TAB_2014 compress for all operations; I have also indexes on this partition. Should I ...
3
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0answers
40 views

Is it possible to get seek based parallel plan for distinct/group by?

An example from this question shows that SQL Server will choose a full index scan to solve a query like this: select distinct [typeName] from [types] Where [typeName] has a non-clustered, ...
0
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1answer
31 views

How can I decide Rebuilding Index with DETAILED or SAMPLED on SQL Server

I want to rebuild my indexes and statistics on DB. How can I select this option on production maintenance. SQL Server Version : Microsoft SQL Server 2012 - 11.0.2100.60 (X64) (Build 7601: Service ...
10
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3answers
13k views

Optimizing queries on a range of timestamps (two columns)

I use postgresql-9.1 with ubuntu 12.04. I need to select records inside a range of time: my table time_limits has two timestamp fields and one property integer. Indeed there are other info columns ...
2
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0answers
41 views

Unique Index much bigger than the table itself

Pg 9.3 on debian 7. I have a very huge table in rows, about 178 million (will turn 250 million in a week and then grow 500 thousand a day), but not that huge in size, wich is 20GB, it's a small ...
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1answer
23 views

Postgres - Insert performance with indexes

We have a table with about 20 columns in a Postgres 9.2.10 DB. For better performance on some SELECT queries, we plan to add an index on one column with data type timestamp. As the index also can slow ...
0
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1answer
15 views

What can cause an Index “total writer” to be the same in every index?

I have a table, with some Indexes ( created by me, others by SQL Server Profiler (SqlServer 2008)). I use this query to analyze unused Indexes: --Possible bad Indexes (writes > reads) SELECT ...
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2answers
191 views

mysql need help optimizing query

I have a table containing servers logs, and another table containing rules to match certain and drop them. The logs tables contains around 1 million rows, and there are about 20-30 rules. The ...
0
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1answer
58 views

Recommended number of index for a table

I've a table with many columns (~70) which contains computer's configuration. It contains approximately 50 000 rows. This table is very requested and all these column too. I use to run the following ...
0
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1answer
199 views

MySQL is using wrong index

This is my table: - user_id INT (foreign key on `user` with the reference `id`) - question_id INT (foreign key on `question` with the reference `id`) - option_id INT (foreign key on `option` with the ...
0
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1answer
13 views

MySQL not using optimum composite key [on hold]

I have a table which I've added a couple of composite keys to: CREATE INDEX idx_foo on my_table(col_one, col_two, col_three); CREATE INDEX idx_bar on my_table(col_one, col_four, col_three); Why, ...
2
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1answer
551 views

Why would the size of MySQL MyISAM table indexes (aka MYI file) not match after mysqldump import?

I've been archiving some MySQL (version 5.0.96) MyISAM tables locally and deleting from my server after checking the data. Every time the process has been pretty similar and comes off mostly without a ...
0
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0answers
27 views

When I can DROP an index safely? [duplicate]

I would like to get rid of unused indexes in my database. I have identified many indexes that are never used (seeks, scans and lookups are 0), and are being updated during DML operations. I used ...
0
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1answer
36 views

One Non-Clustered Index that covers every possible combination of predicates?

Say we have a table against which a number of different queries can be executed and each query has its own combination of predicates. So, for example, if we have a table with columns A, B, C, etc we ...
1
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1answer
717 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? ...
3
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1answer
361 views

2 B-tree indices OR 1 GiST index on tsrange — which will perform better?

I have a table which is storing reservation data using the columns starts_at & ends_at Whenever I'm querying the table to find overlapping reservations, I have an option of using one of the ...
1
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2answers
182 views

Is it a good idea to include a value column (e.g. from measurements) in an index?

Is it a good idea to include a value column into an index for a table which has many million rows? For example a measurement table which looks kind of like this: CREATE TABLE measurements ( id ...
0
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1answer
28 views

Oracle can't drop index with . in name?

I am trying to drop an index that has a dot(.) in its name and can't seem to do it (I'm logged in as the SYSTEM user, which owns the index). Any ideas? SQL> select index_name,owner,status from ...
1
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1answer
268 views

How to repair all indexes in a MySQL database?

My database got corrupted, and now the php app is throwing this error: Invalid query: Can't find FULLTEXT index matching the column list The error is not very useful, since it doesn't say what ...
0
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3answers
412 views

Mysql - How to Optimize Retrieval Time in a Table

I have query like this! which has 200 million Records in a single table.. I am using BTree Indexes in my table... mysql> select COUNT(DISTINCT id) from [tablename] where [columname] >=3; ...
7
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1answer
438 views

Fast hamming distance queries in postgres

I have a large database (16M rows) containing perceptual hashes of images. I'd like to be able to search for rows by hamming distance in a reasonable timeframe. Currently, as far as I properly ...
1
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1answer
25 views

Automatic deduplication (normalization) of strings in MySQL

The question is whether MySQL can use separate physical storage for strings transparently, but with the same operations that are applicable to varchar, including %. I have a large number of ...
1
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0answers
19 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 ...
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1answer
44 views

Poor query performance due to recheck condition on index scan

We are testing the performance of metadata when stored in JSONB compared to a traditional EAV catalogue (commonly used in biomedical scenarios), using a PostgreSQL 9.4 server. I get a problem when ...
4
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1answer
45 views

Does MySQL exectution plan depend on available indexes?

Does MySQL choose an execution plan for a given query taking into account what indexes are available, or does it first choose an execution plan and then uses indexes if they are available? ...
0
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1answer
218 views

Is searching an alternate index on a partitioned myISAM table concurrent or serial?

I have a myISAM table with 30 partitions. The primary key is a SHA1 hash value, which is also used in the partition selection function. I also have an alternate key - an autoincrement integer. Since ...
0
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2answers
20 views

How to tell MySQL to ignore all indexes for a given query?

I've been benchmarking several queries and learning about indexes by using the explain function, profiling and the SQL_NO_CACHE option. My usual benchmarking session goes something like this: SET ...
19
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5answers
15k views

When should I rebuild indexes?

When should I rebuild the indexes in my relational database (e.g. SQL Server)? Is there a case for rebuilding indexes on a regular basis?
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0answers
24 views

Microsoft SQL Server database user permission. that user can not create database [closed]

Grant a user permission that can not create databases. Instead work every thing, like see table work in on it run query. What is meant here is that I wish to create a user who has SELECT privileges ...
3
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3answers
51 views

How does like query work with indexed table

I am working in Spring-java and mysql. I have to query the table of size 100k records. Table has say 10 columns. And In my sql select query I have to make like queries with %text% search on say 4 ...
0
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0answers
61 views

Where are indexes stored in memory and how do they improve performance? [closed]

Where are indexes stored in memory? I am studying indexes in SQL and have not found an exact answer. Can anyone please explain the process? Also, if a table has empid as an indexed column and I want ...
0
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0answers
38 views

Eager Spool 100%

I have a query like below, when I execute it, the parallel query always takes very long time to finish, I found there is index spool(Eager Spool) which costs 100% in execution plan... How can I ...
1
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1answer
47 views

Recommended Postgres settings to speed up indexing on a 100GB database?

I have just installed Postgres 9.1 on a server with 32GB of RAM and 320GB solid-state disk. I will be using this server to serve both my site and my database (i.e. it's not just a database server). ...
0
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1answer
105 views

When to use hashtable over binary search tree vice verse for Database Index

Database Index can be constructed using binary search trees (BST) or HashTables , From my understanding so far , HashTables are superior to BST in terms of time taken for searching and insertions ...
0
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1answer
28 views

How to access the text definition of sql indexes

I am able to access the text definition of stored procedures, views, triggers and functions from sys.sql_modules. I want to get the text definition of indexes. How can I get the text definition of ...
3
votes
1answer
115 views

How to determine cost/benefit of adding an index?

According to Craig Ringer: While it's usually a good idea to create an index on (or including) your referencing-side foreign key columns, it isn't required. Each index you add slows DML operations ...
2
votes
1answer
93 views

Should database be denormalized if I need an index across multiple tables

I have a catalog of album and song names. The song has a foreign key to the album table. I expect queries like: SELECT * FROM song s JOIN album a ON a.id = s.album_id WHERE LOWER(CONCAT_WS(' ', ...
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1answer
363 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 ...
18
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7answers
689 views

Where can I find some guidance on index strategies?

Most of us will probably agree that using database indexes is good. Too many indexes and performance can actually be degraded. As a general rule, which fields should be indexed? Which fields should ...
2
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4answers
2k views

What impact do indexes have on the performance of table modifications? [duplicate]

I have always wondered what the effect indexes have on table modification in SQL Server. Will modification of a table will be slower with an increased number of indexes applied to that table? My gut ...
0
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1answer
1k views

Improve MySQL Query Performance - Too many records

I am using MySQL RDMS for a contact management system. Now a days my database grew in size and contains more than 1 million records. Checking duplicate phone numbers became a big issue during ...
0
votes
1answer
25 views

What does a CONSTRAINT have to do with my unique index?

I have to indexes on my table. The first was created by Django and the second by me. I'm not completely certain what the extra CONSTRAINT means in the first index and am wondering how I would change ...
1
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1answer
81 views

What is an index KEY - emphasis on KEY?

In SQL Server, What does the 'key' part of the phrase 'index key' mean? Is the key a number? what is it? If I have the table of data containing a column called LastNames, and I have, say, a clustered ...
2
votes
2answers
74 views

Is it a good idea to create an index for each column in a new table? [closed]

I will short my question. (SQL-Server 2008) Is it a good idea , when crating a new table, to create an index for each column? Why i'm saying this? Today I was creating a database, and my boss was ...
0
votes
1answer
121 views

Use index intersection feature in mongo 2.6 to compound shard key

I am having three indexes like name,age,salary. I can use them as compound index as per 2.6 (name and age together). But can i use the same indexes as compound shard key like name and age. i also have ...
0
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1answer
28 views

Index for a Postgres query with a sort and an equality

This query is very slow: EXPLAIN (ANALYZE, buffers) SELECT * FROM "Follows" AS "Follow" INNER JOIN "Users" AS "followee" ON "Follow"."followeeId" = "followee"."id" WHERE "Follow"."followerId" ...
2
votes
1answer
30 views

How should a numeric value that is an external key be stored?

This is something I was pondering recently. trying to determine how to store certain values. The best wide spread example I can think of is Federal Employee Identification Number - more commonly knows ...
0
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2answers
69 views

Optimizing a Postgres query with a large IN

This query gets a list of posts created by people you follow. You can follow an unlimited number of people, but most people follow < 1000 others. With this style of query, the obvious optimization ...
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0answers
50 views

Mongo range query became extremely slow on large collection

I have a collection which has 50 million records in it. After using wired Tiger its size became only 3 GB (2 GB data 700 MB index). I have created index on this collection. But when i do a range query ...
1
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1answer
39 views

Performance of Combination lookup

I've been looking into this most of the day and I'm still not getting far so I thought I'd ask on here. Basically its a lottery system and what I need to do is check whether 4 of the 6 balls I have ...