6
votes
2answers
110 views

Improve performance of COUNT/GROUP-BY in large PostgresSQL table?

I am running PostgresSQL 9.2 and have a 12 column relation with about 6,700,000 rows. It contains nodes in a 3D space, each one referencing a user (who created it). To query which user has created how ...
2
votes
1answer
181 views

Can column name be “Group” in Postgresql or in any databases

I was designing a project which specifies that in a table what column name should be and one of the column name in the specification is "group". I tried creating it but it always throw a syntax ...
3
votes
2answers
121 views

How do I use window functions (“over”) together with crosstab in Postgres?

Table: application_app applied_date | applied_class | id -------------------------------+---------------+----- 2013-03-06 15:59:49.22774-05 | BOSFAL13 | 13 2013-05-12 ...
1
vote
2answers
324 views

Avoiding a sort on an already clustered index for group by

On a table T with two fields, pid and did, the following query results in a seq. scan followed by a sort on pid: select count(did), pid from T group by pid Here is the query plan: ...
3
votes
1answer
287 views

Group By primary key or DISTINCT increase query time over 1000x with limit

Also see http://stackoverflow.com/questions/17741167/hibernate-jpa-improve-performance-of-distinct-query but I realized this is mainly a PostgreSQL issue. My application uses a 3rd party extension to ...
1
vote
2answers
103 views

Group Database Entries by time difference

I have a large postgreSQL database with log data. All this data has timestamps and I want to group consecutive rows where the difference between the timestamps is less then 1500 miliseconds for ...
1
vote
1answer
941 views

Error “column does not exist” in a SELECT with JOIN and GROUP BY query

I'm using PostgreSQL 9.1 with a Ruby on Rails application. I'm trying to list the last version of each "charge" (in my history table : hist_version_charges) belonging to the same project id ...
4
votes
2answers
808 views

Postgres: Use result of group by as column names

I have a messages table in a database, which include a sender id and a message type (and of course many more columns not relevant for this question). I try to create a query which counts how many ...
7
votes
6answers
1k views

Find “n” consecutive free numbers from table

I have some table with numbers like this (status is either FREE or ASSIGNED) id_set number status ----------------------- 1 000001 ASSIGNED 1 000002 FREE 1 000003 ...
1
vote
1answer
446 views

postgres GROUP BY and ORDER BY problem

I have two tables like this: CREATE TABLE cmap5 ( name VARCHAR(2000), lexemes TSQUERY ); and CREATE TABLE IF NOT EXISTS synonyms_all_gin_tsvcolumn ( cid int NOT NULL ...
3
votes
3answers
664 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 ...
3
votes
3answers
2k views

Slow query on large table with GROUP BY and ORDER BY

I have a table with 7.2 million tuples which looks like this: table public.methods column | type | attributes ...