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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149 views

MySQL performance of applying unique constraint single column vs combination column

I have a large MySQL InnoDB table containing around 137 million rows. I need to add a unique constraint to the table. We have two options: 1) A combination index on three columns, one of which will ...
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39 views

create_index_cost used_bytes vs alloc_bytes

I'm reading a lot about create_index_cost, but I can't seem to find out why there is such a discrepancy between the size of used_bytes and alloc_bytes. I know what each parameter means, but why is ...
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17 views

Missing index recommendation for an already existing index [duplicate]

SQL Server missing index DMVs suggest to create an index which already exists. The existing one and the suggested one exactly overlap each other; they are single (same) column index with no included ...
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40 views

PostgreSQL indexing table on multiple columns

I have a table that holds half hour metering values in a compact form on a daily basis. The table has a structure as described below: day: timestamp without time zone, // describes a day ...
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26 views

Optimal Table Index for hourly data

I have a table that contains ~40,000,000 records and consisting of the following fields: idName - foreign key relationship to another table Date Hour Type (two possible types) Value Currently I ...
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66 views

Unique Constraint exception after dropping constraint

We had dropped a unique constraint using the ALTER TABLE DROP CONSTRAINT script, but it is still throwing the Unique Constraint exception while trying to insert. We drilled this down to two possible ...
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120 views

Mongodb compound index on two fields where one field is sparse

I have a collection of documents that give stats relating to videos. I have a unique compound index on videoId, date (there is at most one document per video per day). I want to be able to; in a ...
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12 views

Best way to profile SQL Server [closed]

We are developing an email campaign web application for my company. The application is in .Net and we are using Microsoft SQL Server 2012 Web Edition (64-bit). When a big campaign is going out we ...
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1answer
80 views

schema for mysql database with 30million rows

We am building a SaaS backend for restaurants. We integrate directly with POS, so each POS keeps sending customer orders that we store in a following table in mysql. CREATE TABLE name ( `id` ...
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55 views

Does remove document automatically remove the index that reference this document?

I am wondering if removing the document will automatically update the index if this document is referenced?
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37 views

How best to index large table with many index keys

In our datawarehouse load, we bring data in the following manner. 1. from source to stage 2. stage to a consolidation layer 3. from consolidation layer to operational data store (ODS) ...
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23 views

Record in table won't show in form

I have an Access 2010 database that has "frmCatalog" which is sourced from the Catalog table. The Catalog table shows a record with the primary key "Acq" = "5203." But the form does not show 5203. ...
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36 views

Join does not not use index in PostgreSQL?

I have a statement that selects from two tables news and status. It seems that the index on the column status of the table news is not used. This table has about 70.000 rows and the query costs too ...
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92 views

TEMP Tablespace Exceeded when DBMS_REDIFINITION

Oracle Environment. Table size is 500Gb. Free space left on hard drive - 300Gb. TEMP Tablespace is currently 20GB Task: do the DBMS_Redefinition for the table (partition by month) and optimize ...
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1answer
175 views

MySql: Slow join and group by on indexed columns

The following query takes 15-20s to run SELECT "Trade_US"."ID" AS "Trade_US.ID", "Server_US"."Name" AS "Server_US.Name", "Trade_US"."TradeTypeID" AS "Trade_US.TradeTypeID", "Users"."ID" AS ...
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23 views

get mysql index size split by index [duplicate]

I have ran this query : SELECT Table_NAME "TableName", data_length /1024 /1024 "table data_length in GBytes", index_length /1024 /1024 "table index_length in GBytes", ...
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69 views

Measure fragmentation of a single index?

We are measuring the impact of different defrag approaches that we do one index at a time. How do we query to see fragmentation of a single index, by index name (or table + index). This is on SQL ...
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118 views

Does MySQL have a visual tool for suggesting indexes like SQL Server's “Include Actual Execution Plan”?

SQL Server has a remarkably useful feature called "Include Actual Execution Plan" which not only gives you a visual diagram of your query, but also automatically suggests indexes that can improve ...
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372 views

Oracle Text CTXCAT Domain Index, Transactional, and Before Insert/Update Trigger

TLDR: The CTXCAT index is supposed to be transactional, but Before Insert triggers that modify the indexed column don't seem to induce an update. I'm running on Oracle 9i. (Actually, I'm running on ...
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43 views

LIKE or CHARINDEX to check String Contains a Substring [duplicate]

To check a string contains a sub string or not we can use [LIKE] or [CHARINDEX]. I know that like uses indexing in case we have name%.(while %name% may not use index) .Also charindex does not use ...
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142 views

Index intersection issue with Mongo 2.6.4

I upgraded my system with 2.6.4 binaries to use specifically index intersection. But when i tried this my DB got down. I created these indexes in my collection "a_1_b_1" : 1.2 GB, "c_-1" : 500 MB ...
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1answer
140 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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33 views

select where index + other field

Learning indexing I have made an index, consisting of usergroupid and birthdate I understand that queries will then benefit from indexing when searching usergroupid and/or birthdate But what ...
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452 views

MySQL 5.1 -> 5.6 problem, select distinct order by limit query stops using index

I'm testing a MySQL 5.1 -> 5.6 upgrade, and I've run into an issue. I have a query that hits a ~30 million row table, selecting distinct IDs with an order by/limit restriction. Sample query is ...
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71 views

Index on fields with a function

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 ...
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37 views

Mysql table with only two columns, nothing unique: Will an index increase search performance?

If my table only has two columns (username, groupname) and a million or so rows, will an index improve performance at all? Wouldn't it take just as long to search the index file as it would to search ...
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80 views

How to know the correct indexes for mysql?

I tried to find out with explain where I must set the correct index. A current select takes about 20 seconds. Can someone tell me which would be the correct index for my tables? SELECT trade.*, ...
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27 views

Creating a table for indexing another table

We have a table with 350m rows and 12 columns, and around 1m rows adding everyday. We have crappy hardware and we cannot add an index on one of the 12 columns that we really really need to. (severe ...
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31 views

Rebuilding an index not working? [duplicate]

I noticed that when I right click manually on an index and choose "Rebuild" or "Reorganize", its not giving any indication that its doing so, then I click on properties again for the same index, I see ...
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136 views

Can PostgreSQL index calculations be multithreaded?

During a single query write of approximately 300,000 rows with 30 columns all indexed, I noticed that only one core was maxed at a time. Is there any way to calculate indexes multithreaded for single ...
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267 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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158 views

Strange behavior with context index on matarialized view

We are experiencing a very strange behavior with a materialized view on oracle. Here is the statement that we've used to create the materialized view: CREATE MATERIALIZED VIEW MY_MATERIALIZED_VIEW ...
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249 views

NTEXT,Indexing, and lob logical reads

We have an query that would benefit from a covering index but one of the columns that would be returned is a NTEXT data type. I know this can't be added to the index and I also know it would be good ...
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62 views

MySql - multi-column index using only null values from one column

I have a Innodb table with a index that looks at 3 columns. ColA is integer and always has a value. ColB is varchar and always has a value. ColC is datetime and sometimes has a value (NULL). My ...
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140 views

Index to fix this query MySQL

We have an extremely large forum running lots of third party software (Most of which doesn't run all that well) and we're starting to optimize things as time allows. This query keeps popping up in the ...
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232 views

index usages on table with recursive relationship

we are working on a project that uses jpa and oracle. In this project we have a table with a recursive relation: Create table alarm ( id varchar2(200), ... alarmcode varchar2(50), parent_id ...
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129 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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502 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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38 views

I need advise on if I should rebuild my index [duplicate]

I have a SQL Server 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 ...
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451 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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158 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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3answers
200 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
66 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 ...
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444 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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143 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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808 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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779 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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87 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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1answer
54 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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167 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 ...