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
39 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 ...
2
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1answer
43 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
124 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
19 views

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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1answer
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
115 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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0answers
46 views

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
142 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
431 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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0answers
48 views

Need Review - Index Rebuild and Index Reorganize strategy?

I've written a block of code to design Index Reorganize and Index Rebuild strategy based on following recommendation. I'm considering only Clustered and Non-clustered index, not Heap. Does anything ...
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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 ...
5
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1answer
194 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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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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1answer
187 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
93 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 ...
3
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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
72 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 ...
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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
94 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
39 views

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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69 views

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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2answers
56 views

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
231 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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0answers
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
61 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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0answers
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 ...
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1answer
441 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
171 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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17 views

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. ...