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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Walking a BTREE index as far as possible in MySQL

Suppose one has a column of words on which one builds a BTREE index: CREATE TABLE myTable ( words VARCHAR(25), INDEX USING BTREE (words) ); LOAD DATA LOCAL INFILE '/usr/share/dict/words' INTO ...
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1answer
409 views

Can spatial index be a part of a multiple columns index?

This manual over here is extremely unclear and doesn't even provide some sample SQL statements: http://dev.mysql.com/doc/refman/5.6/en/column-indexes.html Another way to rephrase the question is the ...
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2answers
3k views

Postgres full text search with multiple columns, why concat in index and not at runtime?

I've come across full text search in postgres in the last few days, and I am a little confused about indexing when searching across multiple columns. The postgres docs talk about creating a ts_vector ...
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1answer
60 views

SQL Server 2008 Index

What would be the best index(es) to add to the tables in order to make this query as fast as possible. The sd.incidents tables is about 2.5M records, problems about 8K, and changes about 120K. select ...
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1answer
494 views

Tuning queries and indexes using index analysis tool

I've been pointed to this script from several places which apparently helps with designing indexes in Microsoft SQL Server: http://indexanalysis.codeplex.com/ The problem is I'm using Sybase ASA 11, ...
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620 views

Partition Function vs. Clustered Index

We have a table that is clustered on identity/datetime2. It is partitioned on the same datetime2. Are there any reasons to cluster on datetime2/identity instead? I understand the reasoning behind ...
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4answers
828 views

How are foreign key indexes helpful?

How are foreign key indexes helpful? What is the criteria for keeping a foreign key index?
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5answers
283 views

How much does an index need to narrow the results of a search in order to be useful?

How much does an index need to narrow the results of a search in order to be useful in speeding up queries? Some examples all across the spectrum: A column for storing true/false values obviously ...
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3answers
723 views

Is a surrogate key better than a natural key in this case

I copied this code from here: CREATE TABLE records( email TEXT REFERENCES users(email), lat DECIMAL, lon DECIMAL, depth TEXT, upload_date TIMESTAMP, comment TEXT, PRIMARY ...
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3k views

Postgresql 9 speeding up indexed inserts (JPA)

I have an application which generates a lot of data which needs to be inserted quickly (something around 13million records). I use JPA 2.0/Hibernate with Postgres 9.1, and I managed to achieve quite a ...
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1answer
1k views

How are bit fields sorted for an index?

I am building a compound index, and I'm not 100% sure which way to include a bit field that is part of the table. The index will be for something similar to a list of forum topics, where I want the ...
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2answers
134 views

Performance of SQL Server indexing

I want to see the performance differences between an indexed vs non-indexed column when running the same query. The table I've created (FileCollection) is very simple and has the following 3 columns ...
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4answers
6k 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 ...
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3answers
1k views

Detect Index Coalesce

Is there a way to know if a COALESCE has been done on an index? Doing one doesn't seem to update the CREATED, LAST_DDL_TIME, or LAST_ANALYZED attributes. Note: I am not referring to the COALESCE ...
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1answer
1k 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: ...
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2answers
620 views

Computed column with less size than the “referring column”

I have a column with data type nvarchar(max) and I wold like to index this. However, since it's too big it's not possible. So I figured I could create a persisted computed column based on that column ...
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2k views

SQL Server 2005 Index Rebuild/Reorganize

I have checked my huge db and run some shrink tasks for 5 or 7 times. I got about 11 GB freespace. This DB is used for offline reporting operations. Before, when we create a report it was growing ...
4
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1answer
114 views

What is the difference between these two index declarations and do I need both?

I was examining a script with 'Display Estimated Execution Plan' and it made several recommendations for indexes to add to the database. I added them and the script did indeed run much faster. Now ...
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2answers
459 views

If I update a column record in a table, will indexes that do NOT have this column in it be affected?

In terms of performance if I have a table like so: CREATE TABLE [TESTDATA].[TableA]( [Col1] [nchar](5) NOT NULL, [Col2] [nchar](2) NULL, [Col3] [float] NULL CONSTRAINT [TableA_PK] PRIMARY ...
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1answer
608 views

Deleting Rows is Increasing Index Size

We have a very large table in a SQL Server 2008 R2 Standard server which I am archiving rows by copying them into another database on a separate disk and then deleting them from the original table ...
4
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1answer
474 views

Does the order of fields in SELECT query matter when using composite indexing?

I understand that the order of columns in the index itself matters immensely; however, what about the order of columns in the subsequent SELECT queries that make use of that index? For example, if I ...
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2answers
3k views

Index max row size error

Is there a upper bound for an array column? I am getting this error when inserting into the array field - PG::Error: ERROR: index row size 3480 exceeds maximum 2712 for index "ix_data" Here's my ...
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2answers
846 views

Performance degradation after rebuilding indexes

I am optimizing some server application task that uses database (querying, complex calculations, data insertions...). Execution of this task spends about 16 minutes (I have tested it 3 more times) and ...
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2answers
783 views

Index Generation in Postgres

We have a database with a single table made up of around 700 million entries. We update the database by adding new entries on a server then transfer the server to the production server using pg_dump: ...
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2answers
167 views

Spatial index not used

I have a table with a geometry column. For one record, there is only one Point stored. A spatial index has been created but queries searching for the nearest location do not use this index resulting ...
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2answers
101 views

StackExchange clone: where should I add my indexes?

I'm creating an open source stack exchange clone and the following is my schema. What should I add indexes on for it to be optimal? Here is the schema in Rails format (SQL format below as well): ...
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1answer
2k views

How to create an index on an integer json property in postgres

I can't figure out for the life of me how to create an index on a property of my json column which is an integer. I tried it this way (and also dozens of others) CREATE INDEX user_reputation_idx ON ...
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2answers
190 views

Performance of different precedence pseudocolumn solutions with LIMIT

I was wondering about the relative performance of the solutions provided in the answers to a question on stackoverflow, I decided to run some tests. The OP wanted to get the first matching row given ...
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2answers
4k views

Suspended in index rebuild

In SQL Server 2012, an Index Rebuild job is taking a very long time (up to 8 hours). However, not even one Index rebuild completed, so I stopped the index job. In monitoring SQL task: state = ...
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3answers
4k views

SQL Server Timeout: Drop and Recreate Index Solves the Issue

After having sql timeout issues with one of our queries we added a few indices that then made the query run very quickly and got rid of any timeout out issues we were having. The strange thing is ...
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2answers
4k views

MySql - How can I speed up this query

I have the following tables: CREATE TABLE `users` ( `id` int(11) NOT NULL AUTO_INCREMENT, `first_name` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL, `last_name` varchar(255) COLLATE ...
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1answer
1k views

What is Sql Server Clustered Index in Oracle terminology

A clustered index in sql server like a dictionary or telephone directory. A,B,C,D it goes on. If you look up with a name Ozgur you start O then z etc. I would like a simple explaination for this ...
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2answers
168 views

We are running database maintenace with indexing the system, indexing fails due to locking?

We have been trying to do re-indexing in our system, there are users still using the database during the indexing. While doing index for certain tables there is failure of indexing this seems to be ...
4
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1answer
703 views

Why does it take a long time to drop a function based index in Oracle?

I have a function based index that takes 25 minutes to create on a table of 94 Million rows. When I drop the index, it takes 18 minutes. Why does it take so long? I would have thought the drop would ...
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2answers
4k views

Reindexing a large database

I have a very large database (millions of rows) which has been indexed. I receive a diff of rows from another source that I need to update in my database. The problem I am facing is that is it ...
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1answer
1k views

Indexing to improve performance of range queries

I've got a relation in a Postgres 8.2 database similar to this: CREATE TABLE foo ( foo_id varchar(160) NOT NULL, bar_id varchar(160) NOT NULL, created bigint NOT NULL, PRIMARY KEY ...
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1answer
113 views

Proving the usefulness of a specific index

I'm looking for a way to prove that some recently added indexes are positively impacting a production system. I've collected some dmv statistics to show that the indexes are indeed being used ...
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1answer
3k views

When changing the size of a nvarchar column, do I need to drop the unique index? And will the table get locked when recreating the index?

In our database a big table exists that more or less looks like this: CREATE TABLE dbo.production_data ( pd_id BIGINT PRIMARY KEY, serial NVARCHAR(16) NOT NULL UNIQUE, ... ); but now ...
4
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1answer
334 views

How can I alter the fill factor of an index outside of an ALTER INDEX command?

I am using a COTS package to perform index rebuilds across my SQL Server portfolio. The package unfortunately doesn't have an option to set index fill factors globally for an individual instance or DB ...
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2answers
2k views

Index before or after bulk load using load infile?

I have a database with over 1B rows and two columns that are indexed (in addition to the PK). Is it better to have the index pre-defined in the table before the load infile or better to index after ...
4
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1answer
2k views

Is a clustered index locked while a (clustered index) scan is in progress?

The question is pretty simple, as the title says. However, I cannot find any references to confirm or contradict this. The problem leading me to this question is that I have a view joining several ...
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1answer
1k views

Does UPDATE INDEXES work for local indexes?

I have two tables in Oracle 11.2. First is partitioned and has local index (non-prefixed): CREATE TABLE table1 (col1 INT, col2 INT) PARTITION BY LIST(col1) ( PARTITION p1 VALUES(1), PARTITION ...
4
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1answer
789 views

How are indexes represented in an ERD?

What do indexes look like in an Entity Relationship Diagram? I've googled it and I'm unsure what the standard look of an index is in an ERD. And I'm talking about the crowsfoot diagram that includes ...
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3answers
3k views

InnoDB vs MyISAM with many indexes

I am not sure if there is a right or wrong answer to this question, as I suppose it severely depends on the situation, but for the sake of a mental exercise, I'll go ahead and ask it anyway: I have a ...
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2answers
1k views

Should a table have a clustered index even if it doesn't have appropriate fields for it?

If you have a table without a good candidate field or fields for a clustered index (stable, sequential), is it better to have a clustered index on a bad field or is it better to make all table indices ...
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2answers
3k views

Improving performance of nasty nested-view joins

I have a moderate-sized database spread out over a few tables, the rough architecture is: Input Data (Data ID, Session ID and a few fields of statistical importance) Input File (Data ID and a blob) ...
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2answers
2k views

Monitoring Progress of Index Construction in PostgreSQL

Is there a way to monitor the progress of the creation of an index in PostgreSQL. I am creating an index on a large table and I would like to see how fast this is occurring. Is there a way to monitor ...
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2answers
2k views

MySQL: Storing unique URLs

I am creating a table wich will contain user-provided URLs. I want those to be unique, so when the user gives me a URL I will first check if the URL exists and if so return the ID for the entry. If ...
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2answers
196 views

MySQL: Is it safe to have a table with multiple millions of rows?

I have a very complex search query to write that will touch many tables, have conditions and joins. For efficiency reasons, I am strongly considering creating a "cache table" where I would maybe once ...
4
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2answers
171 views

How to create multiple entries on index based on the fields of one row?

I never found a good way to index multiple fields of one row as entries of an index or simulate this feature on MySQL. The problem arises when you have fields working as tags or similar concept. Ex.: ...