PostgreSQL is an enterprise class, open-source, object-relational database management system (ORDBMS) available for all major platforms including Linux, UNIX, Windows and OS X. Please mention your exact PostgreSQL version when asking questions.

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Disk file effects of delete and vacuum

I have a very frequently updated table with 240 million rows (and growing). Every three hours 1.5 million rows are inserted and 1.5 million are deleted. When I moved the cluster to a SSD this bulk ...
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4answers
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tuning postgresql for large amounts of ram

I have two identical servers (in terms of hardware), they are both standard installations of windows server 2008 r2, with minimal software installed (basically my code and required stuff like jvm ...
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2answers
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How to view data in pgAdmin III

I can't believe they make it this hard. I am at a loss about how to view the data in my database. Is there an easy way to see what data is in my tables with pgAdmin III? Alternatively, is there a ...
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PgAdmin III - How to connect to database when password is empty?

I have installed PostgreSQL 9.1 on my PC (Win 7). I have a small Java application connecting successfully to it with login=sa and password="". The connection works. However, it is refused from ...
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3answers
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Combining separate ranges into largest possible contiguous ranges

I'm trying to combine multiple date ranges that may or may not overlap into the largest possible contiguous date ranges. For example: Data: CREATE TABLE test ( id SERIAL PRIMARY KEY NOT NULL, ...
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2answers
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Permission denied in Postgres

I added the user myuserto Postgres. Then I added the database mydatabase in the pgAdmin III GUI and restored from a backup file. So the owner of mydatabase is the superuser postgres. Then I tried to ...
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2answers
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How to turn json array into postgres array?

I have a field user that holds a json document that roughly looks like that: { name: 'foo', tags: ['foo', 'bar'] } What I would like to do is to turn that tags array into a concatenated ...
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1answer
2k views

SQL injection in Postgres functions vs prepared queries

In Postgres, are prepared queries and user defined functions equivalent as a mechanism for guarding against SQL injection? Are there particular advantages in one approach over the other?
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Where does the magic column “name” come from?

I got this by accident: db=> select name from site; ERROR: column "name" does not exist LINE 1: select name from site; ^ db=> select site.name from site; name ...
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1answer
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What is the difference between PostgreSQL 9.0 Replication and Slony-I?

Is there still any use for Slony-I, and if so, what is it? For clarification, from 9.0 Postgresql supports built in streaming replication.
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3answers
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How to convert mysql to postgresql? [closed]

I am desperately looking for a conversion tool to convert a big mysql database to postgresql. I need the tool/script to be: Free Works under Linux Simple to use and not buggy You actually tried and ...
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3answers
389 views

How-to implement an entity with an unknown maximum number of attributes?

I am designing a baseball simulation program and I have run into a problem with designing the boxscore schema. The problem I have is that I want to track how many runs are scored in each inning. The ...
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1answer
342 views

How do I 'hint' the cardinality of a recursive CTE?

I'm using the following recursive CTE as a minimal example, but in general, the optimizer has to use default 'guessed' cardinalities for recursive CTEs: with recursive w(n) as ( select 1 union all ...
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2answers
8k views

Efficient query to get greatest value per group from big table

Given the table: Column | Type id | integer latitude | numeric(9,6) longitude | numeric(9,6) ...
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2answers
3k views

Load balancer versus connection pooling — is there a difference?

I am working on a project that is expected to serve millions of users shortly after launch. The database is postgres, and for now I am assuming at least two servers will be needed. A sys admin (who is ...
9
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1answer
6k views

How to get notices to the output stream?

I have debugging messages in functions. Those message are raised like RAISE NOTICE 'Value of id : %', id; I set my log file with \o messages.txt Then I do what I need to do with \i process.sql And ...
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1answer
6k views

PostgreSQL Database Data File Integrity Check

When running a PostgreSQL database system how do I know my database as a whole has 100% integrity? Basically how do I know if my data files and pages are all 100% good with no corruption? In the ...
9
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1answer
270 views

Busy table is not getting vacuumed

We're using Postgres 9.2 on Windows to store low-frequency timeseries data: we're inserting around 2000 rows per second every second 24 hours, 7 days a week with no downtime. There is a DELETE that ...
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6answers
5k 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 ...
8
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1answer
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Is PostgreSQL replication production ready?

How does PostgreSQL native replication compare to MySQL? I know asynchronous replication has been supported for longer than sync, which is recent. Is synchronous reliable to be used in real projects? ...
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2answers
7k views

For absolute performance, is SUM faster or COUNT?

This relates to counting the number of records that match a certain condition, e.g. invoice amount > $100. I tend to prefer COUNT(CASE WHEN invoice_amount > 100 THEN 1 END) However, this is ...
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3answers
512 views

What is retrieved from disk during a query?

Fairly simple question, probably answered somewhere, but I can't seem to form the right search question for Google... Do the number of columns in a particular table affect the performance of a query, ...
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2answers
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PostgreSQL Index Caching

I'm having difficulty finding 'lay' explanations of how indexes are cached in PostgreSQL, so I'd like a reality check on any or all of these assumptions: PostgreSQL indexes, like rows, live on disk ...
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4answers
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How to check if a subquery has exactly one distinct result and a specified value concisely?

I found myself writing the following: select 'yes' where exists(select * from foo where val=1) and not exists(select * from foo where val<>1); and wondering if there is a more concise way ...
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3answers
1k views

Email address unique or primary key?

I am a newbie in databases. I read around and found out that it's probably not a great idea to use email address as primary key because string comparisons are slower which effects performance in ...
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2answers
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How to get the timestamp column in only milliseconds from PostgreSQL?

I have a column "created" with type timestamp without time zone default now() in a PostgreSQL database. If I select colums, it has a nice and readable format per default: SELECT created FROM ...
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1answer
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postgresql: how do I dump and restore roles for a cluster?

Where are roles stored in a cluster, and how do I dump them? I did a pg_dump of a db and then loaded it into a different cluster, but I get a lot of these errors: psql:mydump.sql:3621: ERROR: role ...
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1answer
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How do I reset the postgres password for PostgreSQL on Windows?

I have installed PostgreSQL on my Windows machine for development. Now I haven't used it for a while, and have forgotten the password for user postgres (default admin user in PostgreSQL). How can I ...
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2answers
627 views

Pros and Cons of Checking if value exist for unique column or let db raise unique error on inserting

While writing a query other day a thought came to me and have stuck in my mind. What is preferable, first checking if a value for a unique column exists and then inserting or insert and let db raise ...
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3answers
26k views

How to solve UTF8 invalid byte sequence copy errors on a restore, when the source database is encoded in UTF8?

I was given the task to migrate a PostgreSQL 8.2.x database to another server. To do this I'm using the pgAdmin 1.12.2 (on Ubuntu 11.04 by the way) and using the Backup and Restore using the ...
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2answers
6k views

Is REINDEX dangerous?

I've been trying to COUNT(*) a table with 150,000 rows that has a Primary key. It tool about 5 minutes, so I figured out this is an indexing problem. Citing the PostgreSQL manual: REINDEX is ...
8
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1answer
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BLOBs or references in PostgreSQL

I need to store binary data files in a PostgreSQL database which runs on an Ubuntu server. Initially there will be a few dozen files of approximately 250kb in size each. However, the number of files ...
8
votes
1answer
371 views

Why are the plans different if the queries are logically alike?

I wrote two functions to answer Day 3's first homework question from Seven Databases in Seven Weeks. Create a stored procedure where you can input a movie title or actor's name you like, and it ...
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1answer
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Why would you index text_pattern_ops on a text column?

Today Seven Databases in Seven Weeks introduced me to per-operator indexes. You can index strings for pattern matching the previous queries by creating a text_pattern_ops operator class index, as ...
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600 views

High Availability for postgresql

I'm new in PostgreSQL database. Recently our developer needed to do some upgrades in our systems. Because of that we are planning to implement some method in order to implement database failover. ...
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2answers
2k views

PostgreSQL: Can I do pg_start_backup() on a live, running db under load?

Our established replication has broken ("requested WAL segment has already been removed" during downtime) We cannot easily stop the master again. Can we do pg_start_backup(), rsync ${PGDATA}/ ...
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6answers
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SQL Query Formatter [closed]

Are there any (Linux based) SQL Query Formatting programs/plugins/extensions? I use PostgreSQL and MySQL but other DB's are welcome as well. I can use a VM to test with but would prefer a Linux ...
8
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2answers
4k views

How to do incremental/differential backup every hour in Postgres 9.1?

Trying to do an hourly hot incremental backup of a single postgres server. I have the following setup in postgresql.conf: max_wal_senders=2 wal_level=archive archive_mode=on archive_command='copy ...
8
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1answer
2k views

How to determine if there are [idle connections with] uncommitted transactions in PostgreSQL?

According to a comment on this question I asked about idle connections in PostgreSQL 9.2, some uncommitted transactions (possibly related to some of those idle connections) might cause some ...
8
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1answer
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PostgreSQL EXCLUDE USING error: Data type integer has no default operator class

In PostgreSQL 9.2.3 I am trying to create this simplified table: CREATE TABLE test ( user_id INTEGER, startend TSTZRANGE, EXCLUDE USING gist (user_id WITH =, startend WITH &&) ); ...
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1answer
2k views

PostgreSQL pg_stat_activity shows COMMIT

We recently replaced our database server with an upgraded machine with 4 x quad core CPUs and 32Gb of ram. We also repurposed our old box to serve as a slave with streaming replication. Both boxes are ...
8
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2answers
3k views

View Postgresql Memory Usage

I'm running Postgresql on a Ubuntu server and need to be able to monitor its memory usage. Currently I have scripts running in a one-minute cron job that monitor/log various statistics and need to ...
8
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2answers
423 views

Biological Sequences of UniProt in PostgreSQL

What is the best way to store UniProt biological sequences in PostreSQL? Data Details We pull in 12 million sequences from UniProt - this number is likely to double every 3-10 month. The length of ...
8
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1answer
2k views

Database archive solutions

In continuation to a question posted by me on Is it a good idea to move high-volume and highly-accessed tables to a separate database?, am looking out for different techniques/solutions available for ...
8
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1answer
12k views

PostgreSQL: permission denied for relation

I'm a bit confused about setting permissions in PostgreSQL. I have these roles: List of roles Role name | Attributes | Member of ...
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2answers
3k views

Can PostgreSQL create a case sensitive database?

I'm porting some code from some version of Sybase to PostgreSQL. This is a C application that uses the Sybase client library. My approach is to write a translation layer that translates calls to ...
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2answers
1k views

Migrate heroku database to Amazon RDS with minimum downtime

I have a heroku postgres database and want to migrate it to Amazon RDS to save cost. What's a way to do so with minimum downtime? Usually this involves replicating database in real time and then ...
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2answers
7k views

PostgreSQL for high volume transactions and for Data warehousing

Am quite new to PostgreSQL, I have never done a large deployment using it before. But, I have good experience in enterprise solutions and I want to try and apply some of what I learned using ...
8
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1answer
1k views

How do I stop/disable PITR and safely clean WAL segments?

Our production server is running PostgreSQL v8.2.3 on CentOS release 5.2 (Final). We've setup PITR in our production server. For some reasons, after setting up PITR, we're not able to manage and ...
8
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1answer
145 views

How do data checksums interact with streaming replication?

Data checksums are a new feature introduced in 9.3, and: there is a new GUC parameter "ignore_checksum_failure" which will force PostgreSQL to continue processing a transaction even if corruption ...