Use this tag for questions about improving the performance and/or efficiency of database queries.

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24
votes
2answers
755 views

How to handle bad query plan caused by exact equality on range type?

I'm performing an update where I require an exact equality on a tstzrange variable. ~1M rows are modified, and the query takes ~13 minutes. The result of EXPLAIN ANALYZE can be seen here, and the ...
2
votes
1answer
45 views

Advice on how to improve the efficiency of a stored procedure using lots of joins

I have a stored procedure that is returning search results for items in a database grouped by customers who own them. The user performing the search is restricted as to what items they can see by ...
2
votes
2answers
2k views

Improve MySQL Query Performance - Too many records

I am using MySQL RDMS for a contact management system. Now a days my database grew in size and contains more than 1 million records. Checking duplicate phone numbers became a big issue during ...
0
votes
2answers
18 views

Combine multiple row's records in one row with MS Access Query?

I have a table (name- tbl2) with 21 column but I want to combine multiple rows records in a row by using a unique reference number as below: Table Field and Records Type Expected Result: Please ...
4
votes
2answers
64 views

Optimized date compare in WHERE clause, convert or datediff=0?

In my query I am comparing two dates in the WHERE clause once using CONVERT: CONVERT(day,InsertedOn) = CONVERT(day,GETDATE()) and another using DATEDIFF: DATEDIFF(day,InsertedOn,GETDATE()) = 0 ...
7
votes
1answer
157 views

Update queries slower after enabling SQL Server Full-Text Index

I have an asp.net website with many insert, update, and delete queries running against my database. A few days ago I create a Full-Text Index on two columns of one of tables. After that I realized ...
2
votes
3answers
77 views

MySQL query takes over a minute to complete

I am trying to pull calls associated with website visits from our huge database... I have got SQL that works, pulls correct results it just takes over minute to complete... Here is the SQL SELECT ...
1
vote
1answer
210 views

Tuning Mysql and Monitoring

I would like to know if anybody can point me towards a tool/way for MySQL database tuning. Actually the tuning of my.cnf is like below: My database engine is MyISAM | Mysql 5.1.73 key_buffer = ...
1
vote
1answer
40 views

How to create an index to be picked by query

I have created multiple indexes one after another, but my query doesn't want to pick them :( CREATE INDEX x ON gan.paid (project_id, country_iso_code, source, date(created_at)); CREATE INDEX x ...
4
votes
3answers
75 views

Make queries and BCP faster on a very large table

This question is somewhat of a continuation to this: Huge data and performance in SQL Server, but different enough to merit its own question. I'm going to copy and paste some of the text from that ...
32
votes
5answers
4k views

Why does adding a TOP 1 dramatically worsen performance?

I have a fairly simple query SELECT TOP 1 dc.DOCUMENT_ID, dc.COPIES, dc.REQUESTOR, dc.D_ID, cj.FILE_NUMBER FROM DOCUMENT_QUEUE dc JOIN CORRESPONDENCE_JOURNAL cj ...
6
votes
1answer
58 views

Is it useful to split a table into a frequently used and a archive table?

I have a table with 1.000.000+ entries. Only the newest 100.000 entries are used very frequently. The other 90% are used very seldom. Is it useful to split this table into a frequently used table ...
2
votes
1answer
200 views

High I/O for part of query

I have a large query that I'm trying to tune. I write lots of queries but haven't done a lot of tuning. I've included a screenshot from SQL Sentry Plan Explorer Free (SSPEF): In the above part of ...
0
votes
1answer
21 views

PostgreSQL 9.4: Index Only Used For Lower INET Ranges

For some reason queries on the high range of are extremely slow and queries on the low range are extremely fast. My index is an adapted version of the answer in Optimizing queries on a range of ...
1
vote
2answers
48 views

Optimising a query to get rows where x is between pairs of values from another table

PostgreSQL 9.4.5 In my database there are 2 tables, vcfentries and exons. I want to query for rows in vcfentries where pos is between a list of pairs of positions, exonstart and exonend in the ...
1
vote
1answer
233 views

MySQL Query with good execution plan is very slow due to Sending data operation

I have the following query: SELECT a.borrowerId AS borrower_id, a.created, NULL AS initiator_team_id, NULL AS initiator_user_id, NULL AS old_team_id, NULL AS old_user_id, ...
2
votes
1answer
61 views

PostgreSQL 9.4 query seems very slow

I'm experiencing a very long response time for a query returning a relatively small number of rows. It takes over three minutes to return ~1.3 million rows. I would assume it was an indexing problem ...
2
votes
1answer
94 views

Subquery ORDER BY doesn't work on MySQL 5.6, but works on 5.5

I try to join 3 tables (products, prices, categories) together to get a result of latest & lowest prices from the joined tables. I was able to get the expected result on MySQL 5.5, but after ...
0
votes
1answer
33 views

Mysql Slow Log when using UNION ALL?

I have following query coming up in mysql-slow log, however i am not sure how to optimized this query and make it much faster. Any ideas on this ? I have already used indexes in following in the user ...
1
vote
1answer
47 views

Vertica performance on select from view with union

We have a huge number of rows(tens of millions), and for each table we have an associated view that is a select with UNION ALL between that table and several others. Now, we are doing a select from ...
1
vote
3answers
159 views

Improve a query using cursor to SET Based approach

I am still new to Query optimisation, and I have a Stored Procedure which uses a Cursor to go through each row within the Table, and performs the following operations: Calculate the Time Difference ...
2
votes
1answer
53 views

SQL Query for Internal Messaging System

I'm creating an internal messaging system (No SMTP/POP3) and I'm looking for a way to query a user's list of messages. Here's my schema: Messages _MessageID (PK) _MessageParentID (if a reply this ...
2
votes
2answers
794 views

Why does innodb_flush_method = O_DSYNC provide such a performance boost with SAN-backed storage?

I've seen some people suggest that O_DSYNC should be used with a SAN. The MySQL docs have this to say about O_DSYNC in general: In some versions of GNU/Linux and Unix, flushing files to disk with ...
2
votes
1answer
158 views

Updating large table worked before, now taking hours

BACKGROUND: I am using a non-production SQL Server to manipulate a large data set and run a few basic calculations. The original data file I have, which is about 30M rows, is missing records (not ...
3
votes
2answers
240 views

How to optimize indexes on MySQL query with various sorts

I have an INNODB table levels: +--------------------+--------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | ...
5
votes
3answers
350 views

Warning about implicit convert

I have table with 2 name columns: CREATE TABLE Test ( TestID int identity primary key clustered , Name_Eng nvarchar(50) , Name_Nat nvarchar(50) ) Now I need a query to get this Name column ...
2
votes
1answer
710 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 ...
3
votes
2answers
172 views

Any SQL where clause performance similar to where 1=0

(i'm using SQL Server 2008R2 or later) For centralize manage and consistent, there is a view definition as follow: CREATE VIEW view_all_situation ( select null as src, tf.col1, sum(col2) as fee, ...
1
vote
1answer
125 views

intermittent performance issue - query with multiple CTE and trashed execution plan

I'm trying to optimize a SQL query that shows variable performance (less than 2 to more than 15s). Overview This is a ColdFusion website, with a SQL Server 2008 R2 backend The query is part of the ...
1
vote
1answer
44 views

What are the cons of implementing faceted search with WHEREs and JOINs?

I'm implementing a filter search system (I understood today that is called faceted search) for an ecommerce website. The fron end looks something like this: Country: [Select a country] Categories: ...
1
vote
1answer
73 views

How to increase performance of UPDATE of ~ 50.000.000 entries

We have a query that uses a temporary table to update certain columns in the database: CREATE TABLE #NEW_OLD ( NEW nvarchar(20), OLD nvarchar(20) ); INSERT INTO #NEW_OLD VALUES ...
1
vote
0answers
68 views

Performance measuring on complex query

Now that I have overworked a very very complex sql statement by going over all those little parts and investigating on their missing indexes, index design, queries column order, join vs. exists... I ...
0
votes
1answer
34 views

Joining 4 tables of which one is unrelated

I have 4 tables as follows. I want to find a wholesum resultset, limited to 25 records, in the following way: Users from Table1 based on a condition And those Users should not be in Table2 [Non ...
2
votes
2answers
48 views

How to unite 2 subqueries to reduce retrieving data from cumbersome tables?

There are 3 tables: user, conversation, message. Table user: id, login, last_login_time (time of last user's login), ... Table conversation: id, user1_id, user2_id, ...
0
votes
0answers
51 views

How to optimize this query on oracle?

I have built this query in oracle to get some data i need from the two tables below. At SELECT REGEXP_REPLACE i get the IN_01 as input parameters from the user and it can be much bigger list than ...
1
vote
1answer
42 views

Performance issue using view vs. direct statement

I have a table with structure similar to this: table values ( id1 int, id2 int, value real, value_at timestamp, constraint primary key (id1,id2,value_at) ) I need to get the "current value" for a ...
1
vote
0answers
40 views

Slow query - PostgreSQL 9.2

I've got a Query that takes some time to be executed... Can you guys help to improve the total time? Thank you! QUERY: SELECT file.inode_id AS file_id, file.parent_inode_id AS ...
2
votes
1answer
33 views

How to optimize this query on Postgres

I'm trying to make a relatively simple query, but it's taking much longer than I'd expect. I have an index in place, but it doesn't seem to be helping much. Here's the query. It sometimes takes up to ...
3
votes
1answer
181 views

Mysql join table order by index

First Master Table CREATE TABLE `edipostingmaster` ( `ID` bigint(20) NOT NULL AUTO_INCREMENT, `applied` int(11) DEFAULT '0', `fileName` varchar(255) DEFAULT NULL, `checkNo` varchar(100) ...
0
votes
0answers
29 views

How to concatenate using cast(collect()) in Oracle DB?

My current query: select distinct mb.BP_TYPE,mb.ABS,mb.BLD_SEQ_CODE, mb.BPCODE||'~'||(select LISTAGG(mbp.PROCEDURE,' ') within group(order by mbp.LINE,mbp.SLN1,mbp.SLN2) from MIS_BS_BB_PROC mbp ...
1
vote
1answer
117 views

Mysql Partitions with Partition limit

I have a partition table on basis of Primary key having 1.5 Billion rows in it. But when i check ibd files only 80 ibd show in GB's whereas 120ibd shows 1MB file. I would like to know how does the ...
0
votes
0answers
21 views

In which order does a mongodump --query executes

In which order does a mongodump --query executes, is from last insert to first insert or the other way around, if it is other way around is there any option that I can pass to mongodump --query, so ...
4
votes
2answers
128 views

slow select query on datetime column

I have a table in MySQL which has approximately 10 million records, and now a query which used to take micro seconds now takes more that 8 seconds to execute! Here is my table structure: CREATE TABLE ...
5
votes
3answers
2k views

Some book suggestions for performance tuning

I am in the process of improving performance on our database application. While I am not a DBA, I am pretty comfortable with SQL. I am after a book that can help me understand how queries written in ...
1
vote
1answer
88 views

Auto update stats turned off for a user database on SQL Server

While trying to improve the performance of few queries, we found via execution plan that there were lot of index / clustered index seeks. Therefore: First thing we did, was to check our Re-indexing ...
0
votes
1answer
28 views

New column to a base table

I want to add a new column to a base table, and add that new column to an existing view... So all selects/updates/deletes translate back to the original table How can I do that? Thanks ...
3
votes
1answer
48 views

Query Plan Error

I have an interesting situation. I use SQL2014 Enterprise version with SP1. The following query results an error message : The query processor ran out of internal resources and could not produce ...
6
votes
2answers
188 views

Effect of an index on update statements where update column is not in an index

I constantly see people say that indexes slow down update, delete and insert. This is used as a blanket statement, as if it is an absolute. While tuning my database to improve performance, I keep ...
3
votes
2answers
60 views

SQL Server “fix” query for Hash Match instead of Nested Loops

At the moment I have a view that is running very slow. It takes about 3 minutes to execute. This suddenly happened. To debug what was going on I used an old dataset and compared both queries. On the ...
1
vote
2answers
4k views

Optimize IN clause in where query with order by - MySQL

I am trying to optimize a query that using IN clause in WHERE to avoid file sorting. To make it easy , I created the following sample which shows the problem. Here is my query: SELECT * FROM `test` ...