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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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 ...
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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 ...
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Naming conflict between function parameter and result of JOIN with USING clause

Given this setup in current Postgres 9.4 (from this related question): CREATE TABLE foo (ts, foo) AS VALUES (1, 'A') -- int, text , (7, 'B'); CREATE TABLE bar (ts, bar) AS VALUES (3, 'C') ...
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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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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 ...
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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 ...
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Can I have one table be an “alias”, or “symlink”, to another?

I have two tables with the same structure, A and B. A certain application is written so that it always writes the same data to both tables. After a discussion with a colleague about the potential to ...
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PostgreSQL 9.1 Hot Backup Error: the database system is starting up

I have been working on a hot backup for Postgres 9.1 for awhile and have run into a consistent issue. After restarting Postgres on the slave server the pgstartup log file and the daily log file under ...
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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 ...
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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 ...
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MongoDB performance vs. PostgreSQL with 5.5 million rows / documents

Can someone help me compare these queries and explain why the PostgreSQL query executes in just under 2000ms and the MongoDB aggregate query takes almost 9000ms and sometimes as high as 130K ms? ...
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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 ...
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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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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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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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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 ...
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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 ...
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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 ...
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Storing and querying rolling data in PostgreSQL

I have a large quantity of weather model data being put into a PostgreSQL database. The machine has 8 cores and 16 GB of RAM. I'm running PostgreSQL 9.3 with PostGIS 2.1. Each table will have a ...
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Avoiding “Row by row” fetch method when dealing with source LOB columns

I have a legacy PostgreSQL database source (ODBC) that I'm attempting to migrate to new SQL Server schema using SSIS. I'm getting a warning saying: 'Row by Row' fetch method is enforced because ...
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SELECT DISTINCT on multiple columns

Supposing we have a table with four columns (a,b,c,d) of the same data type. Is it possible to select all distinct values within the data in the columns and return them as a single column or do I ...
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Are there any professional fulltime PostgreSQL DBA's?

For my job I work on a JavaEE application with PostgreSQL as the database. Although we have a sysadmin for our productions servers, who also manages our database servers, we have no full-time DBA ...
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Set a column's default value to the concatenation of two other columns' values?

I have a Postgresql 8.1 database. In one table, there are three columns: first_name, last_name, display_name. Is it possible to set the default value of display_name to be first_name + " " + ...
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Checking whether two tables have identical content in PostgreSQL

This has already been asked on Stack Overflow, but only for MySQL. I'm using PostgreSQL. Unfortunately (and surprisingly) PostgreSQL does not seem to have something like CHECKSUM table. A PostgreSQL ...
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Database for building a realtime analytics system

I want to build a system similar to Google Analytics (only used for internal use, less traffic and less feature), and mainly focus on Real time counting of unique URI visit/PV by different ...
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Should I invest the time to change the column type from CHAR(36) to UUID?

I have a few million rows in my database already. I didn't know about the PostgreSQL UUID data type when I designed my schema. One of the tables has 16M rows (about 3.5M to 4 M records per shard), ...
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Unexpected Seq Scan when doing query against boolean with value NULL

I have a database column called auto_review where column type is boolean. There is an index for that field, created using the ActiveRecord ORM. CREATE INDEX index_table_on_auto_renew ON table USING ...
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Starting PostgreSQL server after a HDD crash results in FAILED STATE

I am using Fedora 15 with PostgreSQL 9.1.4. Fedora crashed recently after which: An attempt to start the PostgreSQL server : service postgresql-9.1 start gives Starting postgresql-9.1 (via ...
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Concept of Schema in PostgreSQL

I am not able to understand concept and usage of schema in PostgreSQL. I have no idea how it can affect my database design. Why should I use it? Can it affect me in future if I decide to not think ...
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PostgreSQL: Creation date of a table

I've recently finished a project, during which many DB tables were created. Most of these tables contain temporary garbage, and I am looking for a simple way to list all these tables. Is there a ...
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Is it reasonable to mark all columns but one as primary key?

I have a table representing movies. The fields are: id (PK), title, genre, runtime, released_in, tags, origin, downloads. My database cannot be polluted by duplicated rows, so I want to enforce ...
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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 ...
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PostgreSQL PREPARE query with IN () parameters

I'm trying to prepare a query from PHP like: pg_prepare($con, "prep", "select * from test where tid in ($1)"); and then execute it with: $strpar = "3,4,6,8,10"; pg_execute($con, "prep", ...
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Algorithm for finding the longest prefix

I have two tables. First one is a table with prefixes code name price 343 ek1 10 3435 nt 4 3432 ek2 2 Second is call records with phone numbers number time 834353212 10 ...
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Should I use the PostgreSQL bit string?

I've been learning about the bit string data type lately, and I am quite curious about: At the bottom of this doc page there is the sentence: ... plus 5 or 8 bytes overhead depending on the ...
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Finding empty columns of a table in PostgreSQL

What query would return the name of the columns of a table where all rows are NULL?
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What can I do with the new json field?

PostgreSQL 9.2 introduced the json field type. Why and when should I use it? What benefits does it have over a text field? I thought there were new query options available, however I haven't seen ...
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Fast general method to calculate percentiles

I want to find n>1 percentiles of an unsorted column in PostgreSQL. For example the 20th, 40th, 60th, 80th and 100th percentile. An obvious solution is to count and sort the column and then do a ...
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How to determine the sweet spot between pool size and database connections in PostgreSQL

We are having trouble handling the traffic during peak hours to our database server. We're looking into improving the hardware (see this question about that side of things) but we also want to work on ...
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EC2 - How to correctly back up PostgreSQL data?

Here is the setup: 1 small Amazon Linux (EBS-backed) EC2 instance with 3 additional volumes. This is both a web server and database server. One volume for code, one for the PostgreSQL (8.4) data ...
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PostgreSQL: reuse of complex intermediate result in same query

Using PostgreSQL (8.4), I'm creating a view that summarizes various results from a few tables (e.g creating columns a, b, c in the view), and then I need to combine some of these results together in ...
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Replicating some tables from one postgres database to another

I've got the following situation: I have three machines running postgresql databases. One machine holds client account information (call this machine C), the other two machines hold client logging ...
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Equality query on NVARCHAR column yields multiple results in SQL Server 2012

I am in the process of moving a pet project from PostgreSQL (9.2.2) to SQL Server (2012 Standard). I've noticed an interesting phenomenon when querying unicode words. Given the definition: CREATE ...
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Postgresql performed a “fast shutdown” by itself. Why? How was it able to do that?

I've already googled and manual read as much as I could before posting this here. Version info: Postgres8.4 on Ubuntu10.x I have a personal laptop that I run a postgres server on, and a Java script ...
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How can I specify the position for a new column in PostgreSQL?

If I have a table with the columns: id | name | created_date and would like to add a column, I use: alter table my_table add column email varchar(255) Then the column is added after the ...
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Adding nullable column to table costs more than 10 minutes

I have problems to add a new column on a table. I tried to run it a couple of times, but after more than 10 minutes running, I decided to cancel the query because of lock time. ALTER TABLE mytable ...
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What happens in PostgreSQL checkpoint?

Here's part of my checkpoint log: 2014-03-26 11:51:29.341 CDT,,,18682,,532854fc.48fa,4985,,2014-03-18 09:15:24 CDT,,0,LOG,00000,"checkpoint complete: wrote 15047 buffers (1.4%); 0 transaction log ...
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MATCH FULL vs MATCH SIMPLE

I've noticed a MATCH SIMPLE or MATCH FULL option in phpPgAdmin, but I can't find a description in the docs. How do they function? The default is set to MATCH SIMPLE.
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Store a formula in a table and use the formula in a function

I have a PostgreSQL 9.1 database where part of it handles agent commissions. Each agent has his/her own formula of calculation how much commission they get. I have a function to generate the amount of ...
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How to use aes-encryption in PostgreSQL?

I tried aes-encryption by using following statement: SELECT encrypt('test', 'key', 'aes'); which worked, but I am not able to decrypt the value. I inserted it in a field of datatype bytea but I'm ...