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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41 views

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) ...
2
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0answers
15 views

PL/pgSQL - Indexes vs Collation vs Pattern Ops

I'm using PostgreSQL 9.3. Having already read articles and answers on DBA stackexchange: Why would you index text pattern ops on a text column PostgreSQL documentation: Indexes - Opclass Pattern ...
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10 views

Does PGStrom calculate relational 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 doesn't seem to be ...
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1answer
614 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
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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20 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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0answers
14 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
57 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
68 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
28 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 ) ...
4
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1answer
226 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
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", ...
3
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1answer
42 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
38 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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4answers
3k views

Slow query on large table with GROUP BY and ORDER BY

I have a table with 7.2 million tuples which looks like this: table public.methods column | type | attributes ...
2
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2answers
92 views

Update on view over partitioned tables updating all indexes

We have a table, which is partitioned through a date field into separate years. There is a view over all of these tables (Call) Schema is as follows: CREATE TABLE [dbo].[Call_2015]( [calID] ...
3
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1answer
75 views

Total Fragments 99% and I cant get it to stay down [on hold]

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 ...
2
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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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0answers
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
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
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
50 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
97 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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2answers
2k views

Postgres primary key sorted in the reverse order. Will it use the index efficiently?

My Rails database is backed by Postgres database. As you may know, each table in Rails gets assigned a primary key which is of Integer type and is indexed. My list views show records in the reverse ...
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2answers
235 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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0answers
42 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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0answers
22 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 ...
1
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1answer
30 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. ...
0
votes
1answer
71 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 ...
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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 ...
8
votes
2answers
3k views

Does a re-index update statistics?

I've been doing the MS10775A course this past week and one question that came up that the trainer couldn't answer reliably is: Does a re-index update the statistics? We found discussions online ...
2
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1answer
49 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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1answer
194 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
291 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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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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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 ...
2
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1answer
30 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 ...
0
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2answers
48 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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0answers
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
119 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 ...
2
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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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0answers
27 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
52 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. ...
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1answer
148 views

Should I index before or after importing a dump?

I am using mongodb to persist a very big-size (90G), which has nearly 40,000,000 items. I read and parse this file and insert all items into mongodb (my programming language is perl, batch_insert, and ...
3
votes
1answer
59 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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1answer
72 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 - ...