The process of determining which indexes are useful and which are not.

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Intentionally corrupting an index in PostgreSQL

I need to know if there is any method for intentionally corrupting an index in PostgreSQL. I have been searching for it for a long time but never seen anyone mentioning such an act.
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1answer
41 views

How to optimize the sort in Postgres query

I've been trying to optimize the sort in the following query. I ran EXPLAIN ANALYZE and the majority of the time is during the sort when it arranges the output by distance. I've tried converting the ...
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1answer
47 views

Ways to Reduce Database Size and possibly improve performace. Untouched enviroment.

I am new to an environment. The Databases are virtually untouched by a seasoned DBA. I am looking for ways to reduce DB size and possibly improve performance. Unfortunately, I only have WEb edition ...
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1answer
44 views

Row with latest timestamp

How to get the row with the latest value in a TIMESTAMPZ column? Is an index needed? Does an index change the strategy? Would behavior vary by database (I'm using Postgres 9.4)? My app records data ...
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1answer
136 views

Minimizing Page Fetches

I have a complicated database structure and am trying to use it to retrieve Records based on multiple selection criteria from several tables. As a general rule, is it better to attempt to use ...
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2answers
318 views

What is Transaction Path Analysis?

I came across the term Transaction Path Analysis which I am not familiar with. A Google search resulted in only a few results, most of which seem to assume everyone knows what it means. From these my ...
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1answer
127 views

Clustered index on a column with low selectivity

I have a table with a lot of columns. Two lookup functions are performed: 1) lookup by using column name (this happens rarely, maybe twice a season), and 2) lookup by column date. The column name has ...
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2answers
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Separate indices for the field I want to get the MAX() and the ones in the WHERE clause

My customer's database has a gigantic table (hundreds of millions of records) and a SELECT that, by cumulative use, is eating a huge chunk of processing time. Each exec takes almost a minute in ...
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1answer
56 views

Index based on another index [closed]

Assume a mysql table with columns A, B, C, ... . There are one composite index based on columns A+B+C. Combination of values A, B and C is unique, so this index forms the primary key. Now, a second ...
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138 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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1answer
117 views

Excessive CPU use in vendor SQL Server DB

Background: I've got a SQL Server 2012 DB provided by a vendor so modification of queries and tables is limited. We do own the DB though, so we can add and maintain indexes. Indexes haven't been ...
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2answers
201 views

How to optimize indexes on MySQL query with various sorts

I have an INNODB table levels: +--------------------+--------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | ...
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How to do Statistics in Partial Indexes of PostgreSQL efficiently?

This answer motivated think again my following tables but I am still uncertain how to store statistic data for quick selection. I think it is well done with partial indexes because only a subset of ...
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2answers
143 views

mysql multiple column index Cardinality order

How does Multiple-Column Indexes work in MySQL? How is it stored internally? consider a table with Multiple-Column Indexes on two columns (X,Y). If X has High-cardinality than Y i.e., X is less ...
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1answer
434 views

MySQL: Optimize query with a range and distinct count

I have a query on a large table with millions of rows that looks like this: SELECT COUNT( DISTINCT clicks.tx_id ) AS unique_clicks_count , clicks.offer_id FROM clicks WHERE ...
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1answer
61 views

mysql query choosing an incorrect execution plan

I have a primary with an dependant subquery as a where condition that is choosing a wrong execution plan, and therefore is running for ever. Main query: SELECT rtr.id AS id156_, ...
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2answers
33 views

Reorganize Index Task [closed]

Can the Reorganize Index task (maintenance plan or SSIS package) be used to tune performance? Is this an adequate step of triage for degraded application/query performance?
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1answer
45 views

Dropping old and creating a new clustered index

I am wondering what is the best approach for dropping and creating a new clustered index on a table within SQL Server 2008. My primary concern is the length of time it will take to perform this ...
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1answer
296 views

SQL Server 2008 - Question about index behaviour

I have a general question about advanced issues regarding index behaviour. In short, roughly one year ago, we dynamically dropped and recreated a number of indexes with different filters, but using ...
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3answers
102 views

Index optimization and cardinality

I'm by no means a DBA expert. Rather, a Magento developer having to troubleshoot some slow queries. I'll jump right in -- here's my attempt to EXPLAIN the troublesome query: EXPLAIN SELECT ...
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2answers
230 views

how to increase speed of this mysql query?

How I can increase speed of this search query? This search bring news based on time and title and text. each item has own factor. SELECT * , MATCH (`title`) AGAINST ('tax in work') * 1.65 AS ...
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1answer
195 views

PostgreSQL operator uses index but underlying function does not

I'm attempting to use JSONB with JDBC, which means that I have to avoid any of the operators which use the '?' character (as the PostgreSQL JDBC driver has no escaping for this character). Taking a ...
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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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1answer
188 views

Sudden poor SELECT performance on a large table with existing indexes

My company uses a software suite in which the only thing I can truly modify is the database. We've always had performance issues (mostly hardware problems that we hope to resolve soon), but lately ...
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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 ...
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1answer
37 views

Optimize view (and underlying table) for averaging timestamps into hours

I have this table: CREATE TABLE spp.rtprices ( "interval" timestamp without time zone NOT NULL, rtlmp numeric(12,6), rtmcc numeric(12,6), rtmcl numeric(12,6), node_id integer NOT NULL, ...
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1answer
43 views

One Non-Clustered Index that covers every possible combination of predicates?

Say we have a table against which a number of different queries can be executed and each query has its own combination of predicates. So, for example, if we have a table with columns A, B, C, etc we ...
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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 ...
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1answer
450 views

Can indexing views in SQL Server 2005+ speed up SELECT count(*) from a View?

My initial question was How does someone determine if it is a good idea to index a view?. Update: My underlying assumption was that indexing views speeds them up. This is apparently not sensible, ...
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2answers
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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 ...
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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 ...
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1answer
95 views

Index to filter a view before joining the underlying tables [closed]

Using SQL Server 2008 R2 Suppose you have a query like the following select top 1 * from view_cms_user where UserId = 1234 or UserPasswordRequestHash = 'anxazno121o3n' view_cms_user is basically: ...
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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. ...
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1answer
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Indexes in a big table. (About 400 mil of rows)

I have a little deal. I have this table in a SQL Server 2012 Standard edition database. The table contains about 400 mil of rows. CREATE TABLE [dbo].[prodeje] ( [id] [int] IDENTITY(1,1) NOT ...
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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 ...
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Query Performance - Why is a query slower when there are two criteria on the same column?

I have these two queries against a view, where I've added WHERE clauses against a date column (Indexed, Unique, Non-Clustered, Ascending): SELECT ColA FROM MyView a WHERE a.[Date] >= ...
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2answers
160 views

Is there a way I can speed up queries against this particular view?

I have three tables in a PostgreSQL database that I'm querying via a view and some joins. CREATE TABLE network_info ( network CIDR NOT NULL, some_info TEXT NULL, ...
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SQL Server 2005 query with multiple conditions, some indexed, some not

I have a table with 50 million rows. It is indexed on zip. A query Select * from table where zip = '12345' returns 20,000 rows in about 2 seconds When I add an additional condition it jumps to ...
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1answer
232 views

'ERROR: text search dictionary “unaccent” does not exist' during CREATE INDEX?

I'm running PostgreSQL 9.3 on Mac OS X Yosemite. I try to create an unaccent lowercase trigram index. To achieve it I did this: mydb=# CREATE EXTENSION pg_trgm SCHEMA public VERSION "1.1"; ...
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Multiple SQL Server Indexes, which ones to keep?

I am looking at my database that several people have worked on. A particular table is responding slowly when queried on a certain join. I notice some of the parameters of the join are not indexed. ...
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1answer
60 views

Rebuild vs Reorganize [duplicate]

I currently have a maintenance plan that is reorganizing indexes everyday and I would like to know if you reorganize an index everyday would you ever need to rebuild the index? If so, why?
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50 views

MySQL is pretty slow after 50-100k rows whats happen?

i have trying now a lots of time, and i try to find a way there make sense to find out of my problem, but this problem stil make a lot perfumes issues. i testing it of on a developer server ( 2 ...
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73 views

Unique Index much bigger than the table itself

Pg 9.3 on debian 7. I have a very huge table in rows, about 178 million (will turn 250 million in a week and then grow 500 thousand a day), but not that huge in size, wich is 20GB, it's a small ...
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1answer
62 views

Postgres - Insert performance with indexes

We have a table with about 20 columns in a Postgres 9.2.10 DB. For better performance on some SELECT queries, we plan to add an index on one column with data type timestamp. As the index also can slow ...
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27 views

When I can DROP an index safely? [duplicate]

I would like to get rid of unused indexes in my database. I have identified many indexes that are never used (seeks, scans and lookups are 0), and are being updated during DML operations. I used ...
3
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1answer
444 views

2 B-tree indices OR 1 GiST index on tsrange — which will perform better?

I have a table which is storing reservation data using the columns starts_at & ends_at Whenever I'm querying the table to find overlapping reservations, I have an option of using one of the ...
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1answer
172 views

Poor query performance due to recheck condition on index scan

We are testing the performance of metadata when stored in JSONB compared to a traditional EAV catalogue (commonly used in biomedical scenarios), using a PostgreSQL 9.4 server. I get a problem when ...
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1answer
78 views

Does MySQL exectution plan depend on available indexes?

Does MySQL choose an execution plan for a given query taking into account what indexes are available, or does it first choose an execution plan and then uses indexes if they are available? ...
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Index creation issue with MySql and Linux

MySQL Server database is installed on RHEL5.5 and db version is 5.6.20 Community Server. In MySQL database we have a table and it has 11,144 records. I am altering the table and adding index to it. ...
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2answers
148 views

Updating indexes and stats script

I am having the following errors with the script below Msg 102, Level 15, State 1, Line 44 Incorrect syntax near '?'. Msg 319, Level 15, State 1, Line 47 Incorrect syntax near the keyword ...