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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33 views

DB2 10.5 - When inserting, the database is trying to reuse index keys on GENERATE ALWAYS

I am trying to insert a row into a database table which has a GENERATED ALWAYS primary key column. The table has over 1000 rows, and the primary keys start at 1. When I try to do an insert, the error ...
3
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2answers
101 views

Online index rebuild snapshot location and impact of filling index drive

My understanding of a rebuild index online operation is that the index will have a snapshot taken and the rebuild is started on the snapshot index. My question is where does the snapshot index ...
0
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1answer
27 views

What data structure is used for MongoDB 3.x geospatial indexes?

For the MongoDB 3.x geospatial features what structure is used for the indexes? B-tree? R-tree? X-tree? I can't find any information about the structures in their documentation
2
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1answer
84 views

Have foreign key constraint and index key for the same column(s)

I am creating a composite index key for 2 columns and then adding foreign keys to its appropriate table. Do I need to create a multiple index key reference and then create separate foreign keys? My ...
0
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1answer
48 views

How can we drop a constraint without losing the automatically created index?

How can we drop a constraint without losing the automatically created index? If it's possible using a single query.
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1answer
30 views

Hash index for InnoDB

I saw a database schema that looked like this CREATE TABLE foo ( name_hash bigint, name varachar(500), a varchar(500), b varchar(500), ... PRIMARY KEY (name_hash), KEY ... ...
1
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1answer
29 views

How to index an property object in MongoDb?

i've the following sample document: { "_id" : ObjectId("556e177ca43da29e040041a7"), "user_id" : NumberLong(24), "request_datetime" : ISODate("2015-06-02T15:52:12.000-05:00"), ...
3
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1answer
70 views

Drop primary key without dropping an index

Is it possible to drop primary key constraint on a table without dropping the index? I have a situation when I want to remove the PRIMARY KEY to get rid of the NOT NULL constraints and set it to ...
1
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1answer
42 views

DBCC DBREINDEX in MS SQL Server 2008

We have done DBCC DBREINDEX for our production database which size is about 300 gb, it was running for 12+ hours, but i found that DBCC DBREINDEX is obsolete and recommended approach is using ALTER ...
1
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1answer
32 views

Sql Server 2008 : What is the cost of accessing an index?

I've just read this interesting blog post about selectivity notion. In the section 'When is better to not use a database index?', the author states : Accessing the index takes time, and consumes ...
1
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1answer
47 views

Why is MariaDB 10 refusing to use my index on a date field?

I have the following table definition: CREATE TABLE `bets` ( `id` bigint(20) NOT NULL AUTO_INCREMENT, `id_mp` bigint(20) NOT NULL DEFAULT '0', `coin` char(3) COLLATE utf8_unicode_ci NOT NULL, ...
3
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1answer
78 views

How to maintain a global index on a large table undergoing regular partition purges?

Problem I've got giant table haystack weighing in at nearly 3 TB, partitioned by month (date) and subpartitioned by client. I need to create a global index that spans all clients to facilitate ...
0
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1answer
87 views

Estimation of creating index in SQL Server

We create new index on our production database, with a few fields, our database size is around 300GB and it works for one hour and do not finished yet. How can you estimate this operation? If we ...
1
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2answers
55 views

Speed up creation of Postgres partial index

I am trying to create partial indexes for a large (1.2TB), static table in Postgres 9.4. My data is completely static, so I am able to insert all data, then create all indexes. In this 1.2TB table, ...
2
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1answer
48 views

Index fragementation ? is it unavoidable

This is follow up question to @martin smith excellent answer http://stackoverflow.com/questions/1251636/what-do-clustered-and-non-clustered-index-actually-mean After that i have watched MCM video of ...
2
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2answers
94 views

MySQL Index Creation Internals

Right now there are two ways to build an index of a table in MySQL: Create the table structure first, then import the data and add indexes later. Create the table structure with indexes and then ...
1
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0answers
52 views

Postgres not using the index even when rows returned is 5% of the table

I have a postgres table with the following structure: +---------+-------------+-------------+----------+---------+---------+ | id | timestamp | numvalues | text1 | text2 | text3 | ...
0
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0answers
48 views

Is there some tricks to better index a URL column in postgres?

I'm working with a table that needs fast retrieve rows by its url column. But they all will be starting with http://www.: http://www.google.com http://www.amazon.com http://www.stackoverflow.com I ...
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0answers
22 views

Calculate Num_Index_Pages for sizing design

I don't understand Step2 #8 Calculate the number of number of non-leaf pages in the index. I am not sure I understand the "Level". I have Num_Leaf_Pages=508 & Index_Rows_Per_Page=476 I don't ...
0
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0answers
24 views

Trigger copies history table: Will removing index lock options speed up the process?

I have a trigger applied to a table to write inserts and updates to a history table. That history table can grow pretty fast, and we want to see, if we can speed up insert operation a bit. The values ...
0
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0answers
27 views

Postgresql indexing for IS NULL

I have two similar queries, whose only difference (in the last two lines) is that one uses IS NULL while the other compares defined values. Query #1 takes only a few minutes: UPDATE ...
3
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1answer
95 views

CREATE NONCLUSTERED INDEX ONLINE, DROP EXISTING

I want to add three included columns to an existing non-clustered index. With that I'm solving performance issues in the database. Here is some information about the index: Rows: 112 Millions Disk ...
0
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0answers
31 views

Indexing Multiple Possibly Missing Columns

I'm working with a particularly large database, and am not particularly in tune with some of the intricacies of RDBMS's as I work primarily in PHP/WP and with smaller databases. Either way, I have ...
1
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1answer
64 views

Column store index on a large fact table

I have seen column store index and also tested it. I have no doubt admiring that it is lightning fast. But every tutorial and blogs I have considered, says about its limitation "table will become read ...
0
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1answer
15 views

What does MySQL “USE INDEX()” without any arguments do?

Does the USE INDEX() have any effect here? SELECT `posts`.`id` FROM posts USE INDEX() where `posts`.`size` > 1024; (I have it presently in some SQL because of the way the query is ...
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0answers
16 views

MySQL ignores ZWNJ character in string comparison

If you add a unique index to a char columns you can not add two string that differ only in having ZWNJ characters (e.g. 'فا' and 'ف‌ا'). However I need to store both of them. How can I overcome to ...
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1answer
80 views

Help on deciding how to pick Correct Index

I would like to ask for some help to create correct indexes for this query: SELECT DISTINCT D.TypeID FROM dbo.Sizes AS S WHERE EXISTS ( SELECT 1 FROM #PermissionsTable AS PT ...
0
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1answer
48 views

Index Strategy for MySQL Query that matches on one column and between two others

I have a table that contains a set of measurements for a continuous stream of processes. Although each process is individual, they are categorised into groups. The events have a start and end ...
2
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0answers
35 views

How long does the final phase of an online index creation take?

In reading the whitepaper: Online Indexing Operations in SQL Server 2005 it says: The online index build process can be roughly divided into three phases: Preparation Build Final ...
10
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1answer
159 views

How to optimize a query so that it seeks on one index first, and then another index after that

I have two sets of earth measurements from satellite data, each with time fields (mjd for mean julian date) and geography positions (GeoPoint, spacial) and I'm looking for coincidences between the two ...
0
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1answer
45 views

Index cleanup/usage help

My question is this: When running sp_blitz, I get a lot of these 2 warnings/suggestions: Index Hoarder: Unused NC index and Feature-Phobic Indexes: Potential filtered index (based on column ...
0
votes
1answer
95 views

InnoDB Index Doesn't Fit in Memory

I am using InnoDB tables in my database and total index_size is 250 GB and my data size is 500 GB. Server has 128 GB RAM, and innodb_buffer_pool_size is set to 64 GB. Data size is increasing every day ...
0
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1answer
94 views

Optimizing an Informix query — Specify architectural solutions if possible too (like caching service)

We have a huge query on an Informix database that is not performing well. The query is doing a join of 9 different tables. Maximum row count is just 40,000 rows. The query also has 9 sub-queries, and ...
4
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1answer
76 views

PostgreSQL partial index unused when created on a table with existing data

In PostgreSQL 9.3, I am attempting to create an efficient index on a rarely-used (0.00001% of total records) boolean column. To that end, I discovered this post on SO: ...
0
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1answer
40 views

How to determine if an Index is uselss in Percona MySQL?

Using Percona Server 5.5 I've a table which stores user activty (lets call it user_activity). It was created quite a few years ago when I had only a little bit of knowledge about database ...
3
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2answers
73 views

Mysql Index for concat select

For Below Query SELECT MAX(CONCAT(date, ' ', last_entry)) AS LAST_LOG FROM entry_log WHERE TRIM(LEADING 0 FROM card_no)='2948' I've index on date card_no date,last_entry ...
0
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1answer
48 views

Query databases that have MYISAM tables that do not have only fulltext index tables

I am trying to query from the information_schema where the database (table_schema) has MYISAM tables but does not have only fulltext index tables. The statistics tables is very poorly designed for ...
0
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1answer
130 views

Fastest way to disable indices and drop constraints and rebuild SQL Server table

Below are some T-SQL commands that we're running on a table with a few billion records. Most of the database's size is taken up by 5 tables like this. What is the quickest way to perform these steps ...
2
votes
1answer
61 views

Was using `set datcollate='C'` a mistake?

In a pre-production environment running django 1.6 on PostgreSQL 9.1 we had a problem with database records arriving in a different order from what the application was expecting. So we ran this ...
4
votes
2answers
124 views

Optimizing queries on a range of timestamps (one column)

I am using Postgres 9.3 through Heroku. I have a table, "traffic", with 1M+ records that has many inserts and updates every day. I need to perform SUM operations across this table over different time ...
2
votes
1answer
111 views

how to use index to speed up sorting in postgres

I am using postgres 9.4. The messages has the following schema: messages belongs to feed_id, and has posted_at, also messages can have a parent message (in case of replies). ...
-1
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2answers
79 views

When there is a composite index and those columns are in query, does it use index seek? [closed]

I have a table staff having columns, name, year,month and date. I have a composite index on year,month and date. If I have a query like below, will it use index seek scan? select * from staff where ...
2
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0answers
123 views

Why is this MySQL query “using where” instead of “using index”?

Could you help me with this query, please? SELECT p.patid, MAX(c1.eventdate) as eventdate from patient as p left join op_adv_effects._clinical as c1 on p.patid = c1.patid left join ...
0
votes
1answer
39 views

What is the risk of doing a rebuild to my indexes in sql server 2012?

What is the risk of doing a rebuild to my indexes in SQL Server 2012? I have to do a REBUILD, but I don't know what are the risks . The server is running and a lot of information is going in and out. ...
2
votes
0answers
43 views

SQL Server 2005 Datawarehouse DB - Integrity failure caused by NonClustered indexes

Last year I've been working with a data warehouse database (SQL Server 2005) loaded on a daily basis during the nights. Overall database performance is acceptable. However, there is a "known error" ...
0
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0answers
60 views

Composite primary key in Multi-tenant sql server database

I'm building a multi-tenant app (Single database, single schema) using Asp Web Api, Entity Framework and Sql Server/Azure database. This app will be used by 1000-5000 customers. All the table will ...
0
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0answers
8 views

Need a persistent, glorified array / bucket storage solution

I'm looking to create a system that logs information ( think, lots of writes, and a few reads ) in order of entry within a key/value datastore. The order precision is absolutely necessary above ...
0
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1answer
53 views

SQL Server : how can I measure database performance increase after index maintenance?

We are using a SQL Server 2005 database. We currently have no maintenance on our databases indexes. Some of our indexes are showing over 85% fragmentation when looking at the table ...
0
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0answers
32 views

PostgreSQL: raise error if planner needs to do an sequence scan

I want to check if our code does use only indexed columns. I think it does, but I want to be sure. How can I configure/modify PostgreSQL to raise an exception if it needs to do an sequence scan? It ...
0
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0answers
31 views

Optimal index wasn't being used until rebuilt

SELECT COUNT(T1.RECID) FROM LEDGERJOURNALTRANS T1 WHERE PARTITION=5637144576 AND DATAAREAID='abcd' AND JOURNALNUM='abcd-00018' This query gets run numerous times when users view a ...