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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13 views

Best index to apply for modifier query in i2b2

Below is a query being run by a tool called i2b2. I'm unable to change how the query is run. What can I do to the indices in "observation_fact" and/or "modifier_dimension" tables so that this query ...
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10 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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4 views

Does PGStrom calculate index comparisons?

I prefer index calculation and comparison be executed on the GPU. I have stumbled upon PGStrom. It seems one could infer that it will calculate index comparisons, but the claim is not made ...
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1answer
25 views

What is the cost of adding a foreign key in mysql?

I have an application which has a product_def table defining all products. The recrods in product_def are fixed and will never be deleted. CREATE TABLE `product_def` ( `product_id` INT( 5 ) ...
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1answer
43 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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22 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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1answer
35 views

Whats wrong with my index?

I have a table, here is the structure: CREATE TABLE `table_data_cache` ( `id` bigint(20) NOT NULL AUTO_INCREMENT, `date` date DEFAULT NULL, `enterTollgateNumber` bigint(20) DEFAULT NULL, ...
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1answer
65 views

BitmapIndexScan vs IndexScan tuning

I have the following test case: CREATE SCHEMA IF NOT EXISTS long; SET search_path TO long,pg_temp,pg_catalog; CREATE TABLE long WITH (autovacuum_enabled=off) AS SELECT id, (random()*1000)::int AS ...
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1answer
40 views

Using an index for both asc and desc on a string column

I know a trick to make order by queries faster when we want to order by asc and desc. For integers store a negated value. So if I store -7,-11,-8,-5,-1,-2 the order by asc will give -11, -8, -7, 5, ...
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1answer
74 views

Total Fragments 99% and I cant get it to stay down

I have a SQL Server 2008 R2 database it is of size 13000.31 MB and my largest table has around half a million records. It is a database that I have bought. It already has indexes but when I run the ...
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30 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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1answer
37 views

PostgreSQL 9.3: Index on to_char()

How can I index a to_char() of a column? I have tried: adam_db=> CREATE INDEX updates_hourly_idx ON updates (to_char(update_time, 'YYYY-MM-DD HH24:00')); But got the error: ...
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21 views

Checks before Altering a column in SQL SERVER [closed]

What are the checks that has to be done before dropping a column or altering a column.. like dropping the constraints, statistics etc.. on it
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1answer
23 views

Explain doesn't show indexed column as key

Consider the following table structure CREATE TABLE `games` ( `game_id` bigint(20) NOT NULL AUTO_INCREMENT, `players_no` tinyint(4) DEFAULT NULL, `startedon` datetime NOT NULL DEFAULT '0000-00-00 ...
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1answer
20 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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0answers
41 views

I am not able to create/reindex a unique index in a table

I have a table that contains user locations (called public.user_location) and is the following: Column | Type | Modifiers id | ...
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21 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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1answer
28 views

Compare Indexes/Constraints between two SQL Server databases

I have two databases on one SQL Server that I would like to compare Index/Constraints. The two databases should be identical but I have a suspicion that one database is missing a index or constraints. ...
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1answer
44 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
12 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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1answer
70 views

Why isn't this index helping my InnoDB MySQL query?

I'm having trouble understanding why an index I have on one of my tables is doing nothing to help the performance of a JOIN, even when forcing the index. Here is the query: EXPLAIN SELECT * FROM ...
2
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1answer
48 views

Adding Indexes To a Partitioned table in SQL Server 2012

I have recently converted our one large table to use table partitioning in SQL Server 2012. It's a table that stores logs based on a time. So I created a partition function to split the table on my ...
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2answers
96 views

How to add an “INCLUDE” part in an Index Created as a part of CONSTRAINT

I am going through the execution plan of a tsql query. There is a key LookUp (Clustered) in the plan. To avoid this Key LookUp, I tried to Include a column (Status_Ind) to The Index (The Index ...
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2answers
45 views

How to resolve: Specified key was too long; max key length is 767 bytes [duplicate]

Our server is creating a lot of tables and one of them is the Lock_ table. We are using MySQL 5.5 on Percona. Also we are using utf8_general_ci and utf8. It throws the following error when creating ...
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1answer
27 views

MySqlDump's DISABLE KEYS have no effect on import

I have a follow up to my previous question regarding import speed with Inno-Tables (suprise!). Scenario I try to import some big* database dump on my local dev machine in reasonable time. We have a ...
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42 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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1answer
96 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 ...
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0answers
62 views

Can there be any case where it would require additional indexes while all columns compose primary key

Ok i don't know whether this question is asked before or not Here my table SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO CREATE TABLE [dbo].[tblProductPagesFeatures]( ...
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1answer
117 views

Why isn't SQL Server using my non-clustered index and doing a clustered index scan?

Here are my full tables: CREATE TABLE [dbo].[tblCrawlUrls]( [cl_IdUrl] [int] IDENTITY(1,1) NOT NULL, [cl_CrawlNormalizedUrl] [nvarchar](200) NOT NULL, [cl_RooSiteId] [smallint] NOT ...
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26 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) ...
2
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1answer
51 views

Running a query on an improperly indexed, 600gb table

This is my first post on here and I'm really baffled by this. I have joined a team and somewhere in the past a horrific table was created which has been bloated to a point of 600+gb of data. ...
3
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1answer
58 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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0answers
40 views

Indexed query fails to return rows in large (15 billion rows) MyISAM (MySQL) table

I have a very large table (15 billion rows) with a structure like this: CREATE TABLE `textlines` ( `PGUID` binary(16) DEFAULT NULL, `StatID` int(11) DEFAULT NULL, `Time` datetime(3) DEFAULT ...
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42 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 ...
3
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4answers
71 views

postgres: index to SELECT strings like '%foo%';

I have an expensive, periodic PostgreSQL 9.3 query of the form: SELECT * from mytable where name NOT LIKE '%foo%'; foo is actually a constant here that never changes. The query is expensive ...
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1answer
29 views

MySQL FullText search on string shorter than 3 chars returns no rows

I have a MySQL table with some addresses in it. Let's say I have the following 2 rows: "10 Fake Street" "101 Fake Street" I'm trying to use fulltext search with MATCH() AGAINST(). I have set ...
3
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1answer
213 views

Optimizing large database query (25+ million rows, using max() and GROUP BY)

I'm using Postgres 9.3.5 and I have a large table in the database, currently it has over 25 million rows and it tends to get even larger rapidly. I'm trying to select specific rows (all unit_ids with ...
2
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2answers
69 views

Postgresql - Do Foreign Key Constraints Automatically Create Indexes?

Per the PGSQL 9.3 docs: Because this is not always needed, and there are many choices available on how to index, declaration of a foreign key constraint does not automatically create an index on ...
4
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1answer
209 views

Sql Server - Select while insert on another transaction gives unexpected results

I stumbled at situation that changes my knowledge about transactions and locking fundamentally (I don't know much though), and I need help to understand it. Let's say I have a table like this: ...
4
votes
1answer
56 views

Combining full-text and scalar index

Let's say we have a database of 12 million names and addresses that need to be searchable using full-text, but each row contains an integer value too, let's say COMPANYID. The table contains around ...
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13 views

See indices implicitly created for foreign key constaints in MySQL

When I add a foreign key constraint to my table, SHOW INDEX doesn't show any new indices, but the overall space used by the indices in that table increases. Apparently, the index for the field I put a ...
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1answer
53 views

PostgreSQL: Another seq scan where an index scan is expected

Here's the query: SELECT DISTINCT ON(points.track_id) participants.contest_number, points.track_id, points.lat, points.lon, points.alt, points.timestamp, points.h_speed, ...
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1answer
29 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
36 views

Indexing the difference between two columns in MySQL

Is there a way to optimize/index a query that sorts the difference between two columns. I have a modest sized table of 5 million rows that I'm trying to do the following: SELECT pk_column, column_x, ...
2
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2answers
30 views

How to tell which indexes are not being used

Postgresql 9.3 Debian 7 I have a lot of huge indexes in a legacy database I'm trying to optimize. Thinking about dropping all the useless ones, but how can I tell how often they are used and if they ...
4
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1answer
224 views

How to setup complex multi-column index for massive table

I've searched what I could search on Google, SO, etc and haven't found an answer that would seem to fit what I'm looking for. I'm hesitant to make a post about this as I'm sure the answer is out there ...
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1answer
18 views

Index on integer column not helping. Help? (EXPLAIN ANALYZE output inside)

The table market_trades has an integer column market_id which takes values from 1 to 5. This seems like a pretty straightforward query to get the number of trades on each market: WITH markets AS ( ...
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2answers
33 views

Indexing into two “buckets”

I'm creating a database with PostgreSQL that has an integer field called "delay". All of my queries on this column will be checking if the value of this column is less than or equal to 0, or greater ...
3
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1answer
76 views

Does sp_indexoption cause index rebuilds?

I want to switch AllowRowLocks=ON on a number of indexes. Some of those indexes are on large tables, and I don't really want to rebuild or reorganize the index. It is not clear from the MSDN article ...
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0answers
21 views

Why do these two queries (which I think are equivalent) rely on different keys?

We have a query that we don't like, since it ends up doing a full table scan. EXPLAIN SELECT count(*) AS c, location.name FROM study LEFT JOIN location ON study.location_id = location.id ...