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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Spliting Datetime into 2 Columns for Restaurant Reservation Schema?

Using PostgreSQL. The primary driver of this is that while no reservation will exist without a date and time, a user can search for and monitor reservations using a time or date or both. With a ...
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151 views

index for OR operator with different columns

What would be best index for this kind of query: -- id is the PK create table test3(id number,name varchar2(30) not null,lastname varchar2(30) not null); select id from test3 where id=:1 and ...
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294 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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236 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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48 views

What indexes would I create for a query like this?

Here's a query I've got: SELECT "balance_transactions"."fee" FROM "balance_transactions" JOIN charges ON balance_transactions.source = charges.balance_id WHERE "balance_transactions"."account_id" = ...
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1k views

Retrieve Data faster from a huge Oracle Table

I have a huge Oracle table ( ttdinv700 ) which contains almost 20 million rows. I am trying to execute the below query, on the table: select max(ttdinv700.t$trdt) from ttdinv700, ttiitm001 ...
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91 views

Is an explicit KEY redundant if it is covered by a UNIQUE KEY?

I am auditing an application which I've been developing over the course of several weeks. I've noticed this in CREATE TABLE: UNIQUE KEY `baz_3` (`baz`,`foo`,`bar`), KEY `baz` (`baz`), Is the ...
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1k views

Postgres - Optimizing an view dependent on an aggregate function?

I have a table of about 15 million records. Whenever information about a specific charge_id is changed, a new row is added with the current timestamp and the changes. This results in multiple rows ...
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557 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 ...
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60 views

Creating an index on table A but with reference to table B

Our company uses a 3rd party application for numerous aspects of the business. One aspect is dealing with customer payments and when selecting a window within the app to list all the payments ever ...
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187 views

Benefit to keeping a record in the database, rather than deleting it, for performance issues?

So I have a client that I am building a Rails app for....I am using PostgreSQL. He made this comment about preferring to hide records, rather than delete them, and given that this is the first time I ...
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510 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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323 views

Unused Indexes - Consider Primary Key Constraint Supporting Indexes?

I have given a task to find out the unused indexes in my production environment. I'm using a DMV to find the unused indexes should i include the Primary key Clustered Indexes on it? If a Primary key ...
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323 views

Updating an FTS indexed column returns “Invalid InnoDB FTS Doc ID”

Environment: Ubuntu 12.04 (and 13.04) MySQL 5.6.11 I have a table which has a full text index on it (real table has much more columns and rows): DROP TABLE IF EXISTS articles; CREATE TABLE ...
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3k views

Varchar index - will hashing value make it faster?

I have a VARCHAR(1000) column in a table. It will contain strings that will not be guaranteed to be unique. I have a query that searches this column as part of a WHERE IN clause, the list of values in ...
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140 views

Big jump in search time for Postgres Index query for results with high selectivity

I am doing some performance comparison of databases and lucene for full-text searching. So I use Postgres to create an Index for the data to search: CREATE INDEX bodies_index ON bodies USING gin ...
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2k views

Why PostreSQL 9.2 does not use index scan if it can?

My PosgreSQL planner (9.2) does not pick index and rather choose to do seq scan. Here is my table. The index I am talking about is name_left_prefix cwu=# \d web_city; ...
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405 views

SQL Index order and performance based on cardinality and data

I've been working quite a bit on a query that's not operating very efficiently on a DB2 database. The thing will return up to 30k rows or so and take up to 10 seconds. I've been working on getting ...
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574 views

Mysql - How to Optimize Retrieval Time in a Table

I have query 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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330 views

I would like to query a range of criteria on multiple columns in MySQL

I have 3 columns in a mysql table. I'm using Innodb engine. I want to be able to search for some values on those columns and also anything close to those values. For example : We have 3 columns as ...
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427 views

Why do MySQL MyISAM table indexes go out of date?

I have few MyISAM tables, where only the auto_increment primary key is up to date with the number of columns, but not other indexes. Any idea, why this happens?
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199 views

Consolidating indexes

I have one big table that is used to generate business intelligence cube. Currently it has around 40M rows and 55 columns. A lot of the cube dimensions are generated by running 'select distinct' on a ...
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73 views

MySql include partition key in index?

Please look at the following Mysql table: http://pastebin.com/b0NDSbdz I've partitioned the table by sent_at and I'm making sure that most of the queries pass sent_at. do I need to include sent_at in ...
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391 views

Simplify and optimize a complex query

Our site has a chronological event feed that uses MySQL. We have noticed that some of the queries tend to run for quite a bit longer than others. For example, some queries for our heaviest users take ...
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465 views

Mongodb multikey index and $all in queries

I have such structure of documents in my products collection: { title: 'Samsung Galaxy S III', category_id: ObjectId("50bcc2f0b910a6c1936a4424"), properties: [ { title: 'OS', ...
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1k views

InnoDB, What would cause: “db1/tableABC contains 6 indexes inside InnoDB, which is different from the number of indexes 5 defined in MySQL”

MySQL 5.5.24 . We have InnoDB tables that grew almost by double (from 50GB to 100GB - file-per-table enabled) in a few weeks due to a project we are working on. The tables were freshly dumped and ...
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138 views

Simple Slow Query Not Using Indexes

I have a slow query running on a large forum. The EXPLAIN synopsis: mysql> EXPLAIN SELECT COUNT(post_thanks.id) as thanked, post_thanks.postid, post.title, post.dateline FROM ...
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1k views

Issues on defining a PK on a nvarchar column and indexing the FK referring this PK

Someone from the team, has defined two reference tables with a few records in each, and has defined the PK of these tables on a column of type nvarchar(255). The value exists in this columns are ...
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1k views

How to interpret this “db.explain()” for this mongodb query

db.tablebusiness.find({ "LongitudeLatitude" : { "$within" : { "$centerSphere" : [[106.772835, -6.186753], 0.0089967464101566] } }, "indexContents" : { "$all" : ["warung"] }, "Prominent" : { "$gte" : ...
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3k views

Repair with keycache in mysql runs EVERY time. Can't even log why it's happening

I have a MyISAM table w/ ~1million rows and two indexes - one's a three-column key, and the other is a spatial index for bounded SELECT statements on a separate point column. My insert statements ...
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242 views

What is the performance difference between local text index and domain text index in oracle?

What is the performance difference between local text index and domain text index in oracle? Also what is the cost of rebuilding the domain text index when I have to split just one partition? Does the ...
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2k views

At which frequency run CTXSYS.CTX_DDL.OPTIMIZE_INDEX(…) on a fulltext index?

I've been told to run periodically CTXSYS.CTX_DDL.OPTIMIZE_INDEX(...) on some fulltext indexes, with no more information, in particular at which frequency this task should be run. I guess that it ...
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948 views

PostgreSQL 8.4 hangs on create table, reindex

I have a rather small database(200Mb) which was running on ubuntu 10.10/amazon ec2 fine for a year almost but today I ran into the following problem: When I create a table that references other table ...
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303 views

Design Tagging module in the database

I've a database system which we want to define tags for many tables into it. For example I've videos, photos, ... different entities that we wish to make them taggable. The tags could be anything. By ...
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9 views

Increase in IO Wait after adding indexes with postgres

I've recently been put in charge of a system that has been fairly untended for a period of time. The majority of activity is via queued worker jobs based off of data feeds from other systems/data ...
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12 views

What run-time configuration parameters are used for concurrent index creation

Suppose I were to run the following. The first line shows the server's default maintenance_work_mem value. mhildreth=# show maintenance_work_mem; maintenance_work_mem ---------------------- 16MB (1 ...
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27 views

Resolve “stuck” system process of dropping indexes

I am re-vamping some indexes, and have decided to drop 3 on a certain table. The process has been running for almost 2 hours now. The table does have quite a few million rows, but I still feel that is ...
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39 views

Most efficient way to retrieve data by timestamps

I'm using PostgreSQL 9.2.8. I have table like: CREATE TABLE foo ( foo_date timestamp without time zone NOT NULL, -- other columns, constraints ) This table contains about 4.000.000 rows. ...
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30 views

What is the maximum value for the index_length of a MySQL 5.5 table?

I'm trying to find out why a series of inserts is painfully slow (1 minute 15 seconds, on average) on a dedicated MySQL 5.5.47 server, while the same inserts are normally fast (less than 5 seconds) on ...
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28 views

Mongo indexes question

I have the following aggregation query: db.getCollection('usersongs').aggregate([ {$match: { room: 'someObjId', status: { $in: [ "ended", "skipped" ] } } }, {$group: { ...
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53 views

sys.dm_db_index_physical_stats slow on first run after rebuilding indexes

I have a 10GB database in SQL Server 2016 RC1 on Windows Server 2012 R2 where I just performed many insert and delete operations. Afterwards, I ran: EXEC sp_MSforeachtable @command1="SET ...
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68 views

SQL Server : ETL Stage Index

We have a very large staging table (> 80 GB). From our source system we load invoice data in the staging table. From the staging we transform the data and load into DWH/Fact. Every day we delete the ...
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24 views

Postgres odd behavior with indices

I've got a datavalue table with ~200M rows or so, with indices on both site_id and paramter_id. I need to execute queries like "return all sites with data" and "return all parameters with data". The ...
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31 views

MySQL indexing issue when trying to search for a part of a string/word

What we're running into: Engine: MySQL. We've been working on a filter where an user can search for a reference number. However, we've ran into an issue with performance on bigger data sets. We ...
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57 views

Cardinality of an index in a MySQL table is equal to table's row size

I have just included an index to a MyISAM table and the cardinality appears to be 1 million something which is exactly the number of rows in the table. In fact it needed to be 315 because distinct ...
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53 views

Query with join to a table on a different database need an index

I'm creating a query that one of its joins is made to a table from a different database. The query analyzer is suggesting the creation of an index, however I don't have permission to add objects to ...
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57 views

Mysql slow copying to tmp table to indexing

I try to indexing table. The table size is about 60GB. But indexing query is hang on 'copying to tmp table' 18 hours. I found advice setting 'myisam_sort_buffer_size' myisam_sort_buffer_size : 128M ...
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56 views

PostgreSQL doesn't use index on inherited tables

I have two tables in PostgreSQL 9.4.5 deployed on Amazon RDS: an append only, weekly partitioned, All Positions table. These store all position readings from about 100,000 sensors. There are about ...
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81 views

Would adding an INDEX on varchar column in Mysql increase performance?

I have the following table to store log messages: CREATE TABLE `log` ( `id` bigint(20) NOT NULL AUTO_INCREMENT, `timestamp` varchar(40) COLLATE utf8_unicode_ci DEFAULT NULL, `logger` varchar(255) ...
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25 views

How to bucketize using Query optimal bucketization algorithm

I am trying to implement query optimal bucketization algorithm (QOB). The input of the algorithm is D=(V,F) where V is the value of the attribute and F is the frequency of occurrence. For EXAMPLE D ...