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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MYSQL Indexes when looking up on alternating sets of columns

I have a table that looks like: CREATE TABLE `connections` ( `connection_id` bigint(20) unsigned NOT NULL AUTO_INCREMENT, `service_id` smallint(5) unsigned DEFAULT NULL, `parent_id` bigint(20) ...
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3answers
284 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; ...
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2answers
231 views

Minimizing Indexed Reads with Complex Criteria

I'm optimizing a Firebird 2.5 database of work tickets. They're stored in a table declared as such: CREATE TABLE TICKETS ( TICKET_ID id PRIMARY KEY, JOB_ID id, ACTION_ID id, STATUS str256 ...
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2answers
151 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 ...
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1answer
55 views

Multi-row insert vs multiple single row inserts

In my app I do multi-row inserts when I can just because it reduces the number of round trips between the db and the app. However, I was curious, is there any other advantages? For example, if ...
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1answer
266 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 ...
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1answer
2k views

MySQL requires FORCE INDEX on huge table and simple SELECTs

We have an application which stores articles from different sources in a MySQL table and allows users to retrieve those articles ordered by date. Articles are always filtered by source, so for client ...
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1answer
66 views

Should one always VACUUM ANALYZE before REINDEXing in PostgreSQL 8.4?

Early in the morning every day a pgAgent job refreshes the contents of table A from table B on my PostgreSQL 8.4 database. Table A contains around 140k records across 91 columns and has two indexes - ...
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1answer
51 views

MongoDB index strategy

I'm developing a system to back-up computers and store the files / data with retention for a while. The actual files are stored in an object store, while I'm planning to keep the metadata of the files ...
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1answer
43 views

Sybase ASA: Saving and dropping all foreign keys and most Primary Keys for (Bulk) Insert

Background Information: I am trying to migrate from an ASA 12 Database, to a ASA 12 Database by using a Remote Server. I have to migrate a lot of Rows (not all), spread over a lot of tables (not ...
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1answer
95 views

Best Indexing Strategy for Query with Equality[A], Range[B], Group By[C], AND Order By[count(P)]

I have a poorly performing query: SELECT user_id, count(item_id) as count FROM table items WHERE category = 'magazine' AND created_at > 1384754400 GROUP BY user_id ORDER BY count(item_id) desc ...
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1answer
184 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 ...
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1answer
288 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
606 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? ...
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1answer
17 views

How do i increase the total MyISAM indexes?

I have just made a check for my server with mysqltuner. -------- Storage Engine Statistics ------------------------------------------- [--] Status: +Archive -BDB +Federated +InnoDB -ISAM -NDBCluster ...
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1answer
42 views

Optimize Mysql SELECT from 60 milion rows

Task and Problem There are 100 realms and 10k items. An item has many histories. There are 600k histories in each realm. And I want to find all of an item's histories of the last day by using: ...
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1answer
23 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 ...
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1answer
87 views

MySQL - Indexes deleted, reduced column size but table size increases

Here is the original table definition which contains 107547934 (~107.5M) rows CREATE TABLE `twitter_tweets` ( `id_str` varchar(100) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL ...
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1answer
74 views

Tablespace of an index organized table

I want to find the tablespace of an index organized table with primary key. With dba_segments I can only find the tablespace for the primary key. But how can I find the tablespace for the table?
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1answer
208 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 ...
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1answer
59 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 ...
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1answer
122 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 ...
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1answer
51 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 ...
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1answer
54 views

Optimizing a union query

SELECT id FROM user WHERE id IN ( 2,3,4,7,9,21,23,45,324,12,43,254 ) UNION SELECT DISTINCT user_id FROM workgroup_users WHERE workgroup_id IN ( 1,345,34,654,213,123,5,2,3,4 ) I know we should not ...
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136 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 ...
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260 views

Yet another slow query Postgresql 9.3

I'd like to get a count(*) from a relatively small joined table (returned result is about ~30000 rows). I use Postgresql 9.3 so simply getting select count(*) from tasks_task; uses index-only scan, ...
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47 views

What happens when an SSH session is terminated while a query is running?

I have a huge database on a dedicated server, whenever trying to modify the db I use PUTTY to establish an SSH connection and then do the work. Yesterday I started an INDEX query on an innodb table ...
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0answers
59 views

is it good to add index on column used in group by clause?

I have a query like- select x, sum(y) from xyz where z>=100 group by x order by sum(y) desc; will it be faster if I am going to add index on x?
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0answers
54 views

Group by clause giving temporary and filesort

I am using this simple select query which selects data from table inner joins and using group by clause. Here is the query ..I have defined indexes for the where clause and group by clause. But some ...
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0answers
62 views

Understanding how MySQL indexes work

I'm reading this page but I can't get past the following parts: When all tables are processed, MySQL outputs the selected columns and backtracks through the table list until a table is found ...
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0answers
90 views

How does MySQL handle an index if its full size is too large for memory?

Let's assume this (totally artifical) query: select id from T where id%3=0 order by id desc; The index of T (InnoDB) is according to information_schema.tables sized 5 GB and T itself is 3 GB but ...
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0answers
233 views

Using an enum as part of an index definition

When I use an ENUM column in a table the ORDER BY uses the ordinal of the ENUM not its value. I wasn't aware of that. So my question is what are the subtle issues when an ENUM is part of an index ...
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379 views

MySql INNER JOIN doesn't use composite index

I have two tables, table A which contains date and name of table B entry and table B which contains its name and type. Table a has a composite index on table_b_name and date. I'm selecting all table A ...
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0answers
64 views

Error creating spatial index sqlserver

I am creating spatial index on sqlserver table. CREATE SPATIAL INDEX [SIndex_udt_cell_SP_GEOMETRY] ON [udt_cell] ( [SP_GEOMETRY] )USING GEOMETRY_GRID WITH ( BOUNDING_BOX =(80.0713, 26.389581, ...
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0answers
381 views

Is it possible to optimize a range query so an explain statement would state “using index” instead of “using index condition”?

I have a very large table where specific queries made by my application are timing out. The table looks something like this: LargeTable ------------ Id [BIGINT(20)] UtcTimestamp [BIGINT(20)] Pivot ...
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0answers
62 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 ...
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0answers
121 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 ...