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

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1answer
166 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 ...
2
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1answer
24 views

Optimizing indexes

I just began optimizing my schemas with indexes (pretty late I guess). I never dealt with huge dataset but I'll be soon coping with about 1 to 5 millions rows. Here is the schema I'm using right now ...
1
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1answer
180 views

MySQL query optimization with aggregate ORDER BY

I have an analytics table that stores metrics aggregated the day level. I need to ask questions such as "For a given date range and client, what are the most popular items." The schema is as follows: ...
1
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1answer
90 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 ...
0
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1answer
41 views

Best Indexing Strategy for Query with Equality[A], Range[B], Group By[C], AND Order By[count(P)]

I have a poorly performing query: SELECT user_id, count(item_id) as count FROM table items WHERE category = 'magazine' AND created_at > 1384754400 GROUP BY user_id ORDER BY count(item_id) desc ...
0
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1answer
125 views

How to optimize indexes on MySQL query with various sorts

I have an INNODB table levels: +--------------------+--------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | ...
3
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0answers
144 views

How to count selectivity rows in PostgreSQL 8.2

I have problem with two queries on PostgreSQL v8.2. It seem like the optimizer chooses a wrong index: db=# explain select count(*), messagetype, alias from event where templateinfoid = 10 and ...
2
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0answers
56 views

How can one improve the performance of a query that selects on a low cardinality column in MySQL?

I have a "State" column that has a low cardinality (three possible value), on which most of my queries perform an equality selection (WHERE col = 'blah') AFAIK you need something like a bitmap index ...
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0answers
80 views

Can't get rid of filesort on joined query sorting on second table

For some reason, this query: EXPLAIN SELECT * FROM biz as b INNER JOIN listings as l ON b.id = l.biz_id WHERE l.pub_id = 14 AND b.cat_id=310 ORDER BY l.level DESC, l.random DESC LIMIT 5; says it ...
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0answers
403 views

SQL Server Database Engine Tuning Advisor vs DMV queries

What is the best way to tune the indexes on my production database? I normally use the following query : SELECT user_seeks * avg_total_user_cost * (avg_user_impact * 0.01) AS [index_advantage], ...
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0answers
23 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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0answers
26 views

What Index can I apply to a GROUP BY, MIN() and WHERE MySQL Query

I have the following table: CREATE TABLE `wp_prize_draws_log_copy` ( `id` int(11) unsigned NOT NULL AUTO_INCREMENT, `pid` int(11) NOT NULL, `entry_date` date NOT NULL, `entry_time` datetime ...
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39 views

is it good to add index on column used in group by clause?

I have a query like- select x, sum(y) from xyz where z>=100 group by x order by sum(y) desc; will it be faster if I am going to add index on x?
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0answers
98 views

Table Valued Function Very Slow

I have a TVF that when called takes 10 secs to run. However if I take the query inside that TVF, it takes only 1 sec. I have added correct indexes on this underlying query tables. In the Execution ...
0
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0answers
88 views

Howto improve performance for these queries, why is my indexed view making it worse for most of them and how can I change that?

for the record, this is a rewrite of the following question (you do not have to read that because I include all important data here) Howto improve performance for queries against table without primary ...
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54 views

MySQL randomly refuses to use index

Mysql randomly refuses to use indexes for even simple queries. 1 example from slow-query log: # Time: 130904 12:19:59 # User@Host: cron[cron] @ [10.71.41.38] # Query_time: 58.488760 ...
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83 views

one vs two column index difference when doing JOIN query?

Let`s suppose that alfa,beta and gamma contains milions of rows so we need to create indexes obviously to get optimal performace for this query : SELECT * FROM alfa JOIN beta on beta.id = ...