Tagged Questions
1
vote
1answer
22 views
Moving postgresql data directory
I moved postgresql's data directory by following the following steps:
Stop postgres
cp -a source_data_directory destination_data_directory
export PGDATA=destination_data_directory
Changing data ...
1
vote
0answers
25 views
How to Change location of postgres cluster and database within the same machine? [duplicate]
I have my present database cluster of postgres at /mnt/my_hard_drive which I want to change to /home/myfolder. I also want to move all my databases present in the present cluster to /home/myfolder. Is ...
0
votes
1answer
29 views
“relation does not exist” trying to import mysql dump into postgres
environment:
ubuntu 10.04
mysql server 5.1.69
postgres 9.2
Here's the sequence of steps:
created a new postgres database, myDatabase
executed this command: mysqldump -u root -p ...
0
votes
1answer
28 views
String replace using concatenated strings from various columns
I'd like to remove a substring in a column via update statement. The substring to replace consists of multiple strings from other different columns but in strict order.
The specification says:
...
0
votes
1answer
24 views
PostgreSQL created a PostgreSQL user on mac. Is this necessary?
I just installed PostgreSQL on a Mac (Mountain Lion) today.
The installer created a mac user PostgreSQL on my machine. After installation, the user still exists.
My question is that why postgreSQL ...
4
votes
1answer
29 views
How to view the full, flattened query underlying a Postgresql view?
If I have a view on a view on a view (etc.), is there a way to show the full query that this expands/flattens to?
0
votes
1answer
59 views
Select first row (grouping) + add aggregate function
First have a look at this question on StackOverflow.
I'm looking to accomplish the same task, except I also need to add an aggregate function (PostGIS's ST_Union) to my query.
How can I combine the ...
2
votes
1answer
88 views
Postgres: count(*) vs count(id)
I saw in the documentation the difference between count(*) and count(pk). I had been using count(pk) (where pk is a SERIAL PRIMARY KEY) not knowing about the existence of count(*).
My question is ...
1
vote
2answers
54 views
Creating a PostgreSQL SERIAL column using pgAdmin3
When I use pgAdmin3 to create a column of type serial, why does it instead create nextval('prices_id_seq'::regclass)?
Should we keep this type defined by pgAdmin? Manually create the table with SQL ...
1
vote
2answers
47 views
“Rewinding” a Postgresql database
I have heard that Postgresql uses an append-only format for it's databases, and if this is true I should be able to 'rewind' the database to a previous point in time by removing the commits that came ...
0
votes
2answers
67 views
Storing data in PostgreSQL: One table or two?
I've just started using PostgreSQL 9.2 and my data consists of product prices at various points in time, usually a different price every month.
Question: Because every product can have different ...
0
votes
0answers
15 views
Identical Postgres index scan taking 5x longer on server
I have an intermediate table for managing a many-to-many relation between tables called Expert and Subject:
Column | Type | Modifiers
...
0
votes
2answers
84 views
Use CASE to select columns in UPDATE query?
I can use CASE to choose which columns to display in a SELECT query (Postgres), like so:
SELECT CASE WHEN val = 0 THEN column_x
WHEN val = 1 THEN column_y
ELSE 0
END AS ...
0
votes
1answer
24 views
Comparing two tables for a UUID change and fix it
I have two tables which I'm trying to reconcile the differences of in postgresql.
Table A is old and needs updating.
Table B is an updated, schema identical version of Table A which I have the data ...
0
votes
1answer
39 views
Set field values to newly imported rows in PostgreSQL table with existing data
I have a PostgreSQL table with existing data, and needs to import all the rows in a CSV file into that table. I am using pgadmin3's Import tool to do the import.
Question: For the newly imported ...
1
vote
1answer
14 views
Big jump in search time for Postgres Index query for results with high selectivity
I am doing some performance comparison of databases and lucene for full-text searching.
So I use Postgres to create an Index for the data to search:
CREATE INDEX bodies_index
ON bodies
USING gin
...
2
votes
1answer
75 views
Limiting number of results in a Partition using OVER(PARTITION BY)
In the following query, why is it that we have to limit the results returned from each Partition by using the clause WHERE foo.row_num < 3 outside of the subquery foo but not from within the ...
0
votes
1answer
79 views
How to use array variable in query in PostgreSQL
Create table t1 ( xcheck varchar[], name text );
CREATE OR REPLACE FUNCTION fn_acgroup(xch varchar[])
RETURNS record AS
DECLARE xrc as record;
execute 'select name from t1 where xcheck @> ...
2
votes
1answer
34 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 ...
2
votes
1answer
75 views
How to make postgresql SUM to be more accurate on large amount of floating point data?
I'm trying to SUM 8 million floating point (REAL) values with simple query like this:
SELECT SUM(metric) FROM metrics;
However, it returns very inaccurate result.
It should return 137,586.77, but ...
2
votes
2answers
53 views
Postgres RIGHT JOIN with custom array
I'm using Postgres 9.1 and want to get a result with some blanks where there is no data. My query looks like the following:
SELECT institution_id FROM ... WHERE institution_id IN (1, 3, 4, 5, 7, 9)
...
0
votes
0answers
122 views
Achieve PostgreSQL hstore functionality in MySQL
Please suggest any MySQL 5.5+ Engine that can support collection of key-value pairs be stored in any column of a table.
I don't know if this feature is available out of the box in MySQL like ...
3
votes
2answers
125 views
pessimistic locking and client death
We are considering pessimistic locking for our project (SELECT ... FOR UPDATE); as we are used to optimistic locking, we are afraid about the operation of the server being blocked on such a lock (lock ...
3
votes
1answer
67 views
Avoiding repetition without creating a view
Suppose that I have a query Q1 and I need to run a query like the following:
Q1
union
select *
from (some query that uses Q1 outcome)
I would like to do that:
Without creating any view
Without ...
2
votes
1answer
67 views
How to Model / Quickly test for set membership in SQL?
Each row in a table needs to be protected a list of application specific roles lets say something that looks like this example below
Desired Table Structure
pkey | data | roles
...
6
votes
6answers
395 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 ...
2
votes
2answers
297 views
How do I remove duplicate records in a join table in PostgreSQL?
I have a table that has a schema like this:
create_table "questions_tags", :id => false, :force => true do |t|
t.integer "question_id"
t.integer "tag_id"
end
...
1
vote
0answers
155 views
Is there a Postgres admin GUI that can execute a master file containing multiple sql files
I'm developing a really long script. I'd like to break the script into smaller, more manageable scripts and include each sql file in a master file, then just execute the master file.
example: ...
1
vote
1answer
44 views
Script to get duration
I am new to PostgreSQL. I am trying to write a query which can give me duration of the time. The fields are in the format yyyymmddhhmmss. In between we will get empty fields for Start_Time or ...
1
vote
1answer
82 views
How to Reorganize Microsoft Access Table
I have just taken over a retiring DBA's position and is responsible for migrating the current access database to SQL Server or PostgreSQL. Right now, the table structure is a mess. Instead of ...
2
votes
0answers
37 views
What is the equivalent of a “Certificate of Destruction” when using a cloud-hosted database?
We have a Rails application hosted by Heroku and using an Heroku Postgres database. Some of the information we store is considered to be sensitive by our users, and we've been asked if we can provide ...
5
votes
1answer
119 views
How to improve performance on PostgreSQL when using multiple concurrent processes?
Seeing query performance which is not satisfactory on our Python application, which runs several processes that use SQLAlchemy core to access a PostgreSQL 9.2 database. We may have around 100 - 200 ...
0
votes
0answers
135 views
Postgres error ( XX000: invalid memory alloc request size 4294967290 )
I'm getting the following error in my postgres 8.4 database:
XX000: invalid memory alloc request size 4294967290
Operating System : Windows 7 64 bit
Memory : 8GB
Database Version: Postgres 8.4 ...
4
votes
3answers
89 views
Filtering data that could have more than one category
I have a table like the following:
Annotation (
document,
term,
category
)
Where document and term are some ID, while category is an integer.
The couple document - term is not unique, ...
0
votes
1answer
46 views
Faster joining on 'most recent' related rows
I have a bug tracking application. The bug table stores very little,
because every state change to a bug happens by adding a comment. For
example, the current state of a bug is determined by the state ...
4
votes
2answers
115 views
Select longest continuous sequence
I am trying to construct a query in PostgreSQL 9.0 that gets the longest sequence of continuous rows for a specifc field.
Consider the following table:
lap_id (Serial), lap_no (int), car_type ...
0
votes
1answer
44 views
Postgresql: Return Unique Rows
I'm using postgresql and I have a large database. A simplified version of the datastructure for my table looks like this:
id (primary unique key), data, userID
1, foo, 4
2, foobar, 4
3, lala, 5
4, ...
0
votes
1answer
76 views
Permission Denied Copy [closed]
I am a beginner learning how to load data and I can't figure out why I can't load this data into postgres. I am using postgres 8.4 on MAC OS.
copy tname from '/Users/Shared/folder/file.cxv' ...
0
votes
0answers
54 views
Monitoring calculation in xDB replication server in PostgreSQL
I am using PostgreSQL 9.2.
I have installed xDB replication server through stack builder.
I want to know the how much the server slave is lag behind the master.
Master - 192.168.1.2
Slave - ...
1
vote
1answer
157 views
Efficient query plan for selecting all data duplicated on several columns
The flavour in question is PostgreSQL, but it is a generic enough query pattern that your techniques for optimising against other RDBMs should help as well.
The purpose of the query is to show all ...
3
votes
1answer
85 views
Aggregating statistics from child rows
I have a parent row and then many child rows, and I must aggregate statistics from these child rows.
For a more concrete example let's imagine I have one round of golf (parent row) and then child ...
4
votes
1answer
84 views
Does the order of fields in SELECT query matter when using composite indexing?
I understand that the order of columns in the index itself matters immensely; however, what about the order of columns in the subsequent SELECT queries that make use of that index?
For example, if I ...
3
votes
2answers
165 views
Full Text Search With PostgreSQL
i have a table with this rows:
Stickers
------------------------------------------------------
ID | Title |Keywords (ts_vector)
------------------------------------------------------
...
0
votes
2answers
145 views
Using a Select in a Where clause for another Select
I have made a draft remote application on the top of libpq for PostrgreSQL. It behaves well, but I have profiled the general functionning of the application. For each final business result that I ...
2
votes
0answers
119 views
Best book on query optimization, rewriting, refactoring [closed]
I have a specific problem: huge amounts of Web-related data in Postgres db. The queries running against the data are often very inefficient.
But in a more general sense, I need a book that explains ...
0
votes
1answer
317 views
Save output from multiple SQL SELECT commands to a file
Within a Postgres function I would like to run a number of SQL SELECT commands and append the output to the same variable. After all the SELECT commands have run this output should be written to a ...
0
votes
2answers
149 views
ERROR: could not find array type for datatype information_schema.sql_identifier
I am trying to run the below sql command:
SELECT ARRAY(
SELECT column_name
FROM information_schema.columns
WHERE table_name ='gis_field_configuration_stage'
);
and I get the below ...
0
votes
1answer
108 views
MAX function and group by usage - postgresql
I am building a ranking algorithm using IMDB's formula:
http://stackoverflow.com/questions/1411199/what-is-a-better-way-to-sort-by-a-5-star-rating/1411268#1411268
The formula for calculating the Top ...
1
vote
1answer
156 views
Retrieving data from inner join using LIMIT and OFFSET
These are my two tables:
table1
qid[PK] |gid[PK] |abcd | xyz | date
---------------+---------+---------+------+------------
00001 | qwe | 54 | a | 1994-11-29
00002 ...
2
votes
1answer
73 views
sorting groups of related rows by average values while keeping the groups together
I'm using PostgreSQL 8.4, but would like a standard SQL solution if possible.
Consider the following table.
corrmodel=# SELECT * from data limit 1;
id | datasubgroup_id | datafile_id | ...
