2
votes
2answers
191 views

DISTINCT not using an index

I have table (2139868 rows): COLUMN1 NUMBER(20,0) COLUMN2 XMLTYPE COLUMN3 XMLTYPE COLUMN4 VARCHAR2(50 BYTE) COLUMN5 VARCHAR2(50 BYTE) COLUMN6 VARCHAR2(50 BYTE) COLUMN7 VARCHAR2(50 BYTE) COLUMN8 ...
-1
votes
0answers
42 views

Sort warning tempDB spill

I am getting a sort warning tempDB spill with one of my queries, I cant for the life of me figure out how to stop it. I have the following indexes on this table (among many others): (title_nm, ...
10
votes
3answers
288 views

Indexes for SQL query with WHERE condition and GROUP BY

I am trying to determine which indexes to use for an SQL query with a WHERE condition and a GROUP BY which is currently running very slow. My query: SELECT group_id FROM counter WHERE ts between ...
4
votes
2answers
50 views

Spatial index not used

I have a table with a geometry column. For one record, there is only one Point stored. A spatial index has been created but queries searching for the nearest location do not use this index resulting ...
0
votes
0answers
102 views

Yet another slow query Postgresql 9.3

I'd like to get a count(*) from a relatively small joined table (returned result is about ~30000 rows). I use Postgresql 9.3 so simply getting select count(*) from tasks_task; uses index-only scan, ...
0
votes
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 ...
1
vote
2answers
64 views

Indexing varchar column to search for first letter

I'm trying to optimize a legacy web-app where users can ask for a list of all records whose name starts with a given character. The query to optimize is: SELECT oggetto.id_oggetto, titolo, anno, ...
0
votes
1answer
68 views

Index being ignored by Oracle

I have a table for sensor data, simplified it looks like this: DEVICE_ID NUMBER SENSOR_ID NUMBER DATA_TIME NUMBER DATA_VALUE1 NUMBER The table constains billions of rows and is partitioned by week ...
1
vote
1answer
64 views

How is the number of records on a select determined as high or low by optimizer?

What is the threshold between using the index and doing an direct access to the database? I assume this decision is related to the number of index access (and subsequent access to the tables). If this ...
2
votes
2answers
116 views

What can be done to further enhance performance of Multiple Join and Aggregate Queries?

I have a typical star schema simulated here, and I am mentioning two queries: first query simply joins the fact table with 2 dimension tables and 1 calendar table, and the second query joins and ...
0
votes
1answer
72 views

Using an enum index to limit records

A common issue, just not sure on the keywords. I have a table of assessments (14k+ records). Each assessment can be in many different states ('draft', 'proofing', 'amends', etc... and 'done'). Most ...
1
vote
0answers
573 views

How to speed up query on table with millions of rows

The Issue: I'm working on a big table that consists about 37mln rows. Data include measurements of many devices made in certain time e.g. '2013-09-24 10:45:50'. Each day all of those devices are ...
1
vote
1answer
98 views

MySQL looking up more rows than needed (indexing issue)

In our MySQL 5.5 database, we have following InnoDB table with 30M+ rows: +----------------+-------------+-----------------+--------+ | participant_id | question_id | given_answer_id | status | ...
1
vote
2answers
166 views

Optimize simple query using ORDER BY date and text

I have a query to a table in Postgres with an order based on a date field and a number field, this table has 1000000 records The data types of the table are: fcv_id = serial fcv_fecha_comprobante = ...
0
votes
2answers
69 views

Understanding multiple indexes with MySQL (and performance)

I have a "phones" table with around 120 000 records, it contains phone_id, phone_number, phone_user_name, phone_last_contacted, etc. The phone_id is index and looks like: 1,2,3,4 ... 120 000. But I ...
9
votes
2answers
1k views

LIKE uses index, CHARINDEX does not?

This question is related to my old question. The below query was taking 10 to 15 seconds to execute: SELECT [customer].[Customer name],[customer].[Sl_No],[customer].[Id] FROM [company].dbo.[customer] ...
1
vote
1answer
569 views

Query taking non-consistent time to execute [closed]

I have a query which takes large time to execute sometimes.When i checked the speed it was taking 15 seconds.But actually it should run faster than that.When i again checked the query it again ...
1
vote
1answer
255 views

Would adding indexes to my foreign keys improve performance on this MySQL query?

Consider the following query: SELECT `locations`.`id` AS `location_id`, `locations`.`address`, `locations`.`lat`, `locations`.`lng`, `tickets`.`status_id`, `customers`.`name`, ...
0
votes
2answers
270 views

Update performance: clustered versus covering index

I have a simple, 3-column table with about 50 million rows in it. This table gets about 5,000 inserts/updates per second, and perhaps 20 queries per second are executed against the table. The table ...
4
votes
2answers
728 views

Inner join using an array column

Having trouble indexing and executing a query in O (log n) time. The query includes an INNER JOIN, an ORDER BY, and an equality operation. If I understand the laws of databases correctly, a query can ...
2
votes
1answer
55 views

What is the algorithmic complexity of a PosgtreSQL greater than or lesser than index query (compared to equality)?

Assuming there is an index idx_int on an int_col column, what is the algorithmic complexity of a query like this? SELECT id FROM table WHERE table.int_col > 1; I'm specifically interested in ...
6
votes
1answer
274 views

Landed as BI, but databases are a big WTF, what to do?

Maybe a duplicate, but I believe my case is a bit different. From one of the answers I got to this post on SQL Server Central that also comes handy too but is not quite the same scenario: 9 Things to ...
2
votes
0answers
57 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 ...
1
vote
2answers
209 views

Mysql. Block/disconnect slow queries

I am experiencing issue. Someone 'attacked' my server: simply by searching the same phrase with multiple requests. As it is text search request and database indices are not used, the engine searches ...
1
vote
1answer
408 views

Query is not using indexes on third table in left join

My query is not using indexes on third table(pci promotion_coupon_images) . i was tried with using index and force index in query but there is no change in result. any body please suggest me how ...
3
votes
3answers
671 views

PostgreSQL 8.3: Slow GROUP BY on large table

I have a table with about 10 million records. I want to do a simple group by, but it's using a sequential scan and is slow... select run_id, count(*) from result group by run_id; I have an index ...
4
votes
2answers
98 views

Performance of different precedence pseudocolumn solutions with LIMIT

I was wondering about the relative performance of the solutions provided in the answers to a question on stackoverflow, I decided to run some tests. The OP wanted to get the first matching row given ...
2
votes
2answers
165 views

MySQL index on column comparison

How do you go about setting an index to be used for a column comparison like WHERE col1 > col2? col1 and col2 are of DATETIME type.
1
vote
1answer
203 views

Simplify and optimize a complex query

Our site has a chronological event feed that uses MySQL. We have noticed that some of the queries tend to run for quite a bit longer than others. For example, some queries for our heaviest users take ...
2
votes
3answers
208 views

mariadb ignoring force index

I'm trying to tune a relatively simple query: select bt.col1,bt.col2 from bigtable bt join smalltable st on bt.smalltable_id = st.smalltable_id where st.name = 'some name occuring only once in st' ...
2
votes
2answers
1k views

How do I force a JOIN to use a specific index in MySQL?

I have a query that JOINs 2 tables; lineitem and part, select sum(l_extendedprice* (1 - l_discount)) as revenue from lineitem force index for join (l_pk), part where ( ...
2
votes
2answers
218 views

Can I use a foreign key index as a shortcut to getting a row count in an INNODB table?

I have a table that has a large number of rows in it. The primary key (an auto-incrementing integer) is, by default, indexed. While waiting for a row count to be returned I did an EXPLAIN in another ...
3
votes
2answers
71 views

Looking for a possible multi-column index

I have a table highscore containing the columns: game (text) date (timestamp) score (integer) more irrelevant ones... The query most often run on it is: SELECT * FROM highscore WHERE game = ...
3
votes
2answers
443 views

Do I risk losing the benefits of indexing if I have an index on every column?

I use PostgreSQL 9.2. I have a table with ~5 million rows and 150 columns. The table does not change at all (I replace it once a year). Users query this table with all kinds of filters on any some of ...
2
votes
1answer
112 views

Combining columns in index

With reference to RolandoMySQLDBA's answer on MySQL: Index when joining to tables not being used (Performance optimizing question) He mentioned Make sure you build an index that involves the ...
1
vote
1answer
152 views

What would be a optimal index for this query in mysql

I'm trying to optimize this query. SELECT * FROM sales_reps WHERE account_id = 1 AND (state = 'enabled') AND (clients >= 5 OR revenue >= 10000) ORDER BY name, platform, client_group, ...
1
vote
3answers
548 views

Improve performance of a Fact Table

I have a Fact table CardTransactionFact Table Structure TABLE [dbo].[CardTransactionFact] [CardTransactionID] [int] IDENTITY(1,1) NOT NULL, [TransactionTerminalID] [int] NOT NULL, ...
5
votes
2answers
2k views

How can I improve the speed of a query on a 20 million+ row table?

I have a query that is used for getting internet traffic statistics of certain IP addresses. There are separate IP address fields for hosts and blocks of IPs called assignments. The data is stored ...
3
votes
2answers
721 views

How does compound index help speed up query?

Say we have a bunch of column in mysql table. Latitude Longitude Say we make an index (Latitude and Longitude) Well, the index will sort by Latitude first and IF the Latitude is the same it'll sort ...
1
vote
1answer
889 views

postgres composite index design

In my rails application using the Postgres database, I have a table called tw_schedules which belongs to a scenarios table (one scenario to many tw_schedules). In addition to the scenario_id foreign ...
2
votes
1answer
135 views

Should I use an index or a hash function on a primary key if I have 100000 rows of data?

I have a table named PRODUCT that has 100,000 rows. I was wondering if either indexing, or a hash function on the primary key would result in better performance. I was also hoping someone could ...
9
votes
3answers
757 views

Can spatial index help a “range - order by - limit” query

Asking this question, specifically for Postgres, as it has good supoort for R-tree/spatial indexes. We have the following table with a tree structure (Nested Set model) of words and their ...
7
votes
1answer
220 views

Performance of query with a range condition and order by

We have the following table (in SQLite on Android) which a tree structure (Nested Set model) of words and their frequencies: lexikon ------- _id integer PRIMARY KEY word text frequency integer ...
1
vote
1answer
778 views

Index Strategies on Text or NVARCHAR(MAX) Fields

I have the following query (simplified for question) I'm trying to speed up for a read only DB ... SELECT [sysid] ,[Date]=CONVERT(CHAR, DATEADD(D, [date], '1800-12-28'),101) ,[From]=[from_addr] ...
0
votes
1answer
128 views

Creating Indexes to optimize query

I have this query and I want to increase its performance by adding appropriate Indexes. DELETE FROM MYTAB1 WHERE MYID1 IN ( SELECT MYID2 FROM MYTAB2 ); I am not familiar with the ...
5
votes
2answers
824 views

Why does MySQL choose this execution plan?

I have two queries, select some_other_column from `table` order by primary_index_column asc limit 4000000, 10; and select some_other_column from `table` order by secondary_index_column asc ...
0
votes
2answers
181 views

Attempting to avoid SORT in query planner

I have a query that is used VERY frequently in my application. Without modifying the query itself, I'm trying to optimize it by toying with different indexing schemes. Here's the query (basically): ...
4
votes
2answers
3k views

MySql - How can I speed up this query

I have the following tables: CREATE TABLE `users` ( `id` int(11) NOT NULL AUTO_INCREMENT, `first_name` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL, `last_name` varchar(255) COLLATE ...