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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When REBUILDing indexes on SQL Server, what bearing does tempdb & LOG disk speed have?

Say I have the a data disk that is 50x faster than the LOG and tempdb (measured by Random Write speed) disk. (Don't ask why that's something we'll be fixing if needed) I have a table that's got 19 ...
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450 views

Recreate Indexes on 1 billion record table

I have a table with over 1 billion records and it has 6 indexes (including Clustered index (ID)). I need to partition this table on a new Clustered index with date column. I have just enough space ...
5
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2answers
133 views

Indexing strategy for dynamic predicate

Assume SQL Server 2012 Standard edition. My database has a table with 500 million rows. The table has about a dozen columns, none of which are very wide (some varchar(100)'s and some ints). The ...
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190 views

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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260 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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1k 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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56 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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333 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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336 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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5answers
269 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
488 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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4answers
566 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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3k views

When to add indexes to #temp tables?

When testing stored procedures in SSMS, it sometimes says there is a missing index on #someTempTable____________________000000000000005B] (someField) etc etc When I do add them like this to the sp: ...
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1k 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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3answers
2k views

Hard and Fast rule for include columns in index

Is there any hard and fast rule to decide what columns and in which order it should be put in Included in non clustered index. I was just reading this post Why use the INCLUDE clause when creating an ...
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3answers
2k views

Why does MySQL ignore the index even on force for this order by?

I run an EXPLAIN: mysql> explain select last_name from employees order by last_name; +----+-------------+-----------+------+---------------+------+---------+------+-------+----------------+ | ...
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321 views

Custom unique column constraint, only enforced if one column has a specific value

Is it possible to have a custom unique column constraint as follows? Suppose I have two cols, subset and type, both strings (though the data types probably doesn't matter). If type is "true", then ...
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5answers
2k views

Improve sort performance in PostgreSQL?

I've got a simple blog database in postgres-8.4 which has two tables, articles and comments. I have a query (generated by Django) that wants to get the latest article of type 'NEWS' and also find the ...
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2answers
111 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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2answers
916 views

Index on primary key not used in simple join

I have the following table and index definitions: CREATE TABLE munkalap ( munkalap_id serial PRIMARY KEY, ... ); CREATE TABLE munkalap_lepes ( munkalap_lepes_id serial PRIMARY KEY, ...
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3answers
938 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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2answers
303 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 ...
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1answer
108 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
130 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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180 views

How can a fill factor of 0 or 100 be the same?

As of my understanding, Fill factor of 80 implies that 20 percentage of each leaf-level page will be empty to enable future growth. I can't correlate how fill factor of 0 and 100 can be the same! Am I ...
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185 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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608 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
557 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
49 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 ...
4
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1answer
164 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 ...
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3answers
3k views

Optimizing queries on a range of timestamps (two columns)

I use postgresql-9.1 with ubuntu 12.04. I need to select records inside a range of time: my table time_limits has two timestamp fields and one property integer. Indeed there are other info columns ...
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2answers
97 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
1k views

Rebuilding index has impact on mdf/ldf files SQL Server 2008

While rebuilding index have used option 'SORT_IN_TEMPDB = ON' in order to avoid unnecessary growing your user database files. What does it exactly means? Is complete process done on TempDB and does ...
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2answers
600 views

Slow ORDER BY with LIMIT

I have this query: SELECT * FROM location WHERE to_tsvector('simple',unaccent2("city")) @@ to_tsquery('simple',unaccent2('wroclaw')) order by displaycount I'm happy with it: "Sort ...
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2answers
3k 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
749 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
123 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
959 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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3answers
80 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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2answers
650 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
830 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 ...
4
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1answer
465 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 ...
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1answer
373 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 ...
4
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2answers
848 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
159 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.: ...
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1answer
87 views

Database having only db_datareader shows invalid properties for a index

If a SQL server database user has only public permission in server roles and for a particular database only db_datareader and public permission then while trying script index as CREATE To option in ...
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1answer
298 views

Why would you index text_pattern_ops on a text column?

Today Seven Databases in Seven Weeks introduced me to per-operator indexes. You can index strings for pattern matching the previous queries by creating a text_pattern_ops operator class index, as ...
4
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1answer
165 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 ...
4
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1answer
300 views

Using indexes to create multiple relationships to a table in order to enforce data integrity and add meaning

I'm working on an inventory database that uses supertype/subtype model. My question regards creating multiple relationships with the same tables using the primary key and composite indexes that also ...