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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196 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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2answers
944 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
votes
1answer
1k 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
633 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
454 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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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 ...
4
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2answers
169 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
162 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.: ...
4
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1answer
145 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 ...
4
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1answer
714 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
341 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 ...
4
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2answers
437 views

Does a cluster index provide more benefits than pre-sorting the load file and creating non-cluster index?

Informix 11.70.TC4DE: CREATE TABLE cluster_tbl ( fk_id INT, data CHAR(2048) ); LOAD FROM "presorted.ld" INSERT INTO cluster_tbl; CREATE UNIQUE CLUSTER INDEX cl_idx ON cluster_tbl(fk_id); ...
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3answers
2k 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 ...
4
votes
2answers
3k views

SQL Server 2008R2 - Why is my index not used

I have a table defined in the following way: CREATE TABLE [dbo].[MyTable] ( [MyTable_ID] [int] IDENTITY(1,1) NOT NULL, [COLUMN_WITH_DATA] [varchar](128) NOT NULL, [COLUMN_A] [varchar](128) ...
4
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2answers
162 views

Does a dual key or single key lookup perform better on a table with a lot of data?

We have table where rows unique between 3 columns. GroupA, GroupB, ProductID. GroupA & GroupB are used in combinations to Group sets of ProductIDs and will always be used to lookup sets of ...
4
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2answers
550 views

Less RAM than Index_length MyISAM

I'm working on a database to store "time series" data (the value of X was Y at this time). The rows themselves are very small and static in size, with the primary key consisting of two smallint ...
4
votes
1answer
915 views

Storing hex values as strings or integers?

I've inherited a database that uses sets of 32-byte hex strings to attempt to uniquely identify objects. Each string is called a fingerprint and each object can have up to 20 fingerprints. I'm ...
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2answers
2k views

Determine Index Compression Candidates Online

By doing the following I can determine if an index will benefit from compression and how many columns should be included in the compression: ANALYZE INDEX Owner.IndexName VALIDATE STRUCTURE OFFLINE; ...
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2answers
350 views

Should I use a composite or single-column index?

I have the following columns in my database table (Medicines). ID bigint, MedicineName nvarchar(50), BrandName nvarchar(50), MedicineCode nvarchar(20), and price,quantity. I am making a stored ...
4
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2answers
319 views

What happens to the index of a primary key after a DROP CONSTRAINT?

I am running PostgreSQL 9.1.4. I have a table with many existing rows, and a bunch of other tables with foreign keys pointing to it, for which I am trying to : 1 - Remove the pkey constraint on the ...
4
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2answers
637 views

Why index REBUILD does not reduce index fragmentatation with a page count > 1000?

This is kind of a followup to the existing question on this site "Why index REBUILD does not reduce index fragmentatation?". The accepted answer to that question, and all other resources I have found ...
4
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1answer
811 views

How does SQL Server choose an index key for a foreign key reference?

I am working with a legacy database that was imported from MS Access. There are about twenty tables with non-clustered, unique primary keys that were created during the MS Access > SQL Server upgrade. ...
4
votes
1answer
126 views

Filtered indices: Why include the filtered-on field?

This just drives me mad. Consider a simple table with irrelevant columns removed: create table boxes ( row_id int not null identity(1,1) primary key, location varchar(15) null, dismantled bit ...
4
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1answer
205 views

Strictly only RAM matters?

I have to work on a project which would have a extra large table with billions of records but only two fields one is id and another is text. And id would be set to BIGINT and PK then if 8+2 (extra 2 ...
4
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1answer
1k views

SQL Server 2008 R2 reindex job reorganise getting stuck

I am currently experiencing this job getting stuck in my nightly maintenance solution - ALTER INDEX [PK_ThirdPartySettleCalled] ON [evo_archive].[dbo].[ThirdPartySettleCalled] REORGANIZE WITH ...
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2answers
6k views

SQL Server: index creation date

In SQL Server 2005 and above, how can I find when an index was created?
4
votes
1answer
346 views

Indexes file damaged, was on ramdisk

I have put some of my indexes into a filegroup that contains one file, that file is on the ramdisk, the performance is great, but the problem is that the file was deleted incorrectly (the file ...
4
votes
2answers
983 views

Inner join using an array column

Having trouble indexing and executing a query in O (log n) time. The query includes an INNER JOIN, an ORDER BY, and an equality operation. If I understand the laws of databases correctly, a query can ...
4
votes
1answer
156 views

After Rackspace server creation, PostgreSQL query planner doesn't work as expected

We created an image of one of our database servers in Rackspace. Then, we created a new server using that image, expecting things to work. However, the index performance we have seen seems to be ...
4
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1answer
1k views

Indexing strategy when using the between operator SQL Server 2008

I have a large table ~25 million rows with the structure CREATE TABLE [dbo].[rx]( [pat_id] [int] NOT NULL, [fill_Date] [date] NOT NULL, [script_End_Date] AS ...
4
votes
1answer
3k views

Should I rebuild index after truncate/large insert?

I have a stored procedure that truncates some tables with around 1.75M rows in each, before inserting new data (based on data in other tables, calculations etc.) Basic outline is very simple: ...
4
votes
2answers
957 views

Could running ANALYZE on all databases on large InnoDB tables show some performance increase?

So we have an old database that was fragmented until we ran OPTIMIZE on all tables. The database/tables are about 100GB in size. Tables are InnoDB with heavy read/write activity. There are so many ...
4
votes
4answers
442 views

Can I reorganise index on a sql server 2005 database without performance hit on production server

I would have preferred to run online index rebuild instead but our production sql server (2005) is standard edition. Hence I think I am left with reorganising index and update statistics after that. ...
4
votes
1answer
7k views

Unique index corrupted SQL. Select query returns single row but create unique index fails

I am not able to repair my database due to below errors, when I run dbcc checkdb(DBNAME, REPAIR_ALLOW_DATA_LOSS) I am getting the errors listed here. When I run a select query for these key values, ...
4
votes
1answer
870 views

How to index dynamic attributes in MongoDB

I have following kind of data (simplified a bit from my real case) in MongoDB: { "name":"some name", "attrs":[ {"n":"subject","v":"Some subject"}, {"n":"description","v":"Some ...
4
votes
0answers
249 views

SQL Server Deadlock - Two SELECT Exclusive Locks on Exact Same Index and Key [closed]

How is the deadlock graph below possible? How did two SELECT statements simultaneously acquire an exclusive lock on the exact same resource? The exclusive locks were on the primary key index for ...
4
votes
0answers
99 views

Rebuild Index Task removed WHERE clause from filtered index [closed]

I have a filter index setup on a table as follows: CREATE UNIQUE NONCLUSTERED INDEX [IX_TableName_Column_Filtered] ON [Schema].[TableName] ( [Column] ASC ) WHERE ([Column] IS NOT NULL) WITH ...
4
votes
1answer
209 views

MySQL table design of logging tables

I'm not a DBA by any means, but I have a basic understanding of some of the underlying principles of database optomization. Currently we have a table that logs session data, it writes about ...
4
votes
1answer
918 views

SQL Server 2008 query planner failing after index drop & recreate

Recently we ran a script to our production DB that would dynamically drop and recreate hundreds of indexes as filtered indexes. While this script had run perfectly in all other previous tests, now ...
3
votes
4answers
573 views

indexing on multiple nvarchar(max) columns

I have multiple nvarchar(max) columns in my DB named ShipperName,ConsigneeName, ProdDesc,BillOFLading. What I need to do is to have UNIQUE INDEX for the combination of these columns. As I am failed ...
3
votes
1answer
718 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 ...
3
votes
2answers
1k views

Should I refresh query plan cache

Please let me explain my problem and situation: I have a web application - MVC3, MSSQL Server 2005, LinqToSQL. It has been running great until one fine morning I pushed a lot of rows to a table that ...
3
votes
2answers
478 views

Do I risk losing the benefits of indexing if I have an index on every column?

I use PostgreSQL 9.2. I have a table with ~5 million rows and 150 columns. The table does not change at all (I replace it once a year). Users query this table with all kinds of filters on any some of ...
3
votes
3answers
637 views

Does this computed CHECKSUM() index design make sense?

I have come across what looks to me like a slightly odd pattern in a SQL Server 2005 database I'm taking care of, and was wondering whether it's just me, or whether it really is odd. There are a ...
3
votes
3answers
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 ...
3
votes
2answers
437 views

Performance impact of having gaps in Identity Column in SQL Server 2005

We have a number of tables in our database with an identity column as the primary key & clustered index. Over the years records have been added and deleted from these tables and of course there ...
3
votes
2answers
1k views

How does Oracle handle composite index lookups?

MySQL cannot use a composite index in a lookup in which the WHERE condition doesn't include the columns forming a left-most prefix: MySQL cannot use the index to perform lookups if the columns do ...
3
votes
4answers
811 views

How to check for existence of an INDEX on a column independent of used SQL database

Is there are unified way of how to check for the existance of an INDEX for a given column irregardless of the actual SQL database system used? For MySQL one could for instance check for the existance ...
3
votes
3answers
213 views

Is there a way to execute sql statement in sql server based on sql server version?

I would like to create computed index on a table if sql server is 2008 or newer and a simple index if sql server is 2005 or older: -- check for sql server version if (select ...
3
votes
1answer
172 views

How to update views outside of update/insert transaction in SQL Server

Looking at SQL Server indexed views I see that these views are updated within a transaction that updates dependent tables. I wonder if there is a way around it? There will be about 10 views with 20 ...