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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4
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2answers
99 views

Multi-row insert vs multiple single row inserts

In my app I do multi-row inserts when I can just because it reduces the number of round trips between the db and the app. However, I was curious, is there any other advantages? For example, if ...
1
vote
0answers
22 views

export data to xml by the use of query to xml then importing it using xpath

i have use QUERY_TO_XML function in order to export data to xml , after that i want to export this data. this data might contain reserved chars in the xml tags like "' & ..." ex electrical ' ...
0
votes
0answers
46 views

Concurrent SELECT and UPDATE in multiprocessing python

I have to randomly match about 20 million rows in two tables without using the same row twice using PostgreSQL 9.3.5. Both tables have the following structure CREATE TABLE de_sim_points_end ( -- ...
0
votes
0answers
38 views

What minimum RAM should the server have for a Django application with Postgresql server?

I have a Django application. The database is Postgresql with 8GB size. We are also using Nginx with gunicorn. Will a 4GB server be enough for good performance ( like on Digital Ocean) ? I was under ...
2
votes
1answer
42 views

What does the Postgres <-> operator do?

I was reading through the Postgres documentation on materialized views and in one example they use the following: SELECT word FROM words ORDER BY word <-> 'caterpiler' LIMIT 10; I tried to ...
1
vote
2answers
57 views

How to create a temporary table using VALUES in PostgreSQL

I am learning PostgreSQL and trying to figure out how to create a temporary table or a WITH declaration that can be used in place of regular table, for debugging purposes. I looked at the ...
0
votes
0answers
19 views

Possible to get log file with only statements sent to Postgres from my app (and not from psql prompt)?

I'm using an ORM in my app and would like to see all statements sent to Postgres so that I can figure out exactly what the ORM is doing. In the Postgres config file I added log_statement = 'all' to ...
0
votes
1answer
25 views

How can I aggregate multiple results from another table using something like BOOL_AND?

I'm using PostgreSQL as my database. CREATE TABLE users ( id SERIAL NOT NULL, name TEXT NOT NULL, PRIMARY KEY (id), UNIQUE (name) ); CREATE TABLE groups ( id ...
0
votes
2answers
64 views

insert inserted id to another table

Here's the scenario: create table a ( id serial primary key, val text ); create table b ( id serial primary key, a_id integer references a(id) ); create rule a_inserted as on insert to a do ...
0
votes
0answers
28 views

What should be the ideal network configuration for a Postgresql Streanming Replication and PgPool HA setup

I have the following configuration using Pgpool, Postgresql with streaming replication. Pgpool is used for load balancing and automatic failover. .-----. .--------. | | ...
2
votes
1answer
2k views

Sharding Postgres Database

I have a Postgres database that has grown to the size where it is no longer feasible to store everything on a single database node. There is a Customer table in my schema where each row represents a ...
1
vote
1answer
51 views

Performance of single vs multiple column unique constraint

I'm using PostgreSQL 9.3. I want to understand if I have an option to make a constraint unique across the entire table vs. unique across a subset of the table (i.e. by using 2 columns in the unique ...
1
vote
1answer
29 views

Table-based custom type does not verify check constraints

Is there any way for a table-based custom type to obey the table check constraints, other than creating my own type based on the table? Assume the following table that serves as a source for the ...
3
votes
1answer
2k views

How to remove known elements from a JSON[] array in PostgreSQL?

I'm facing an issue regarding using the JSON data type in PostgreSQL. I try to achieve storing a Java model denormalized in the DB. The model features lists of complex objects. Thus, I decided to ...
2
votes
1answer
66 views

Get products of category plus all child categories till leaf nodes

We have a hierarchy which looks this: Now the problem is that most products are only connected with 1 category, which is most of the time the lowest level. I am trying to get ALL products below a ...
2
votes
1answer
88 views

Recursive CTE to find unique slug

I have an article table where I want the slug to be unique. CREATE TABLE article ( title char(50) NOT NULL, slug char(50) NOT NULL ); When the user enters a title e.g. News on Apple, I want ...
0
votes
1answer
30 views

How can I create a bool column for a view based on the result of a statement?

I'm using PostgreSQL as my database. CREATE TABLE groups ( id SERIAL NOT NULL, name TEXT NOT NULL, PRIMARY KEY (id), UNIQUE (name) ); CREATE TABLE users ( id ...
3
votes
1answer
187 views

Add NOT NULL constraint to large table without table scan

Trying to add a NOT NULL constraint to a table with 1 billion rows. I cannot afford a table lock for more than a couple of seconds. Is there a way to prevent a full table scan during the alter table ...
0
votes
1answer
47 views

Postgresql csv to db translate foreign keys

I'm trying to import data from a csv to a postgresql database. the db table looks like this: CREATE TABLE texts( text_id serial PRIMARY KEY, topic_id integer REFERENCES topics, format_id integer ...
2
votes
1answer
95 views

SELECT query with DISTINCT on a table-structure for graphs is very slow

I have 2 tables where nodes contains about 60m rows and edges about 500m rows (both growing fast). These two tables represent a directed graph. CREATE TABLE edges ( node_from bigint NOT NULL, ...
3
votes
1answer
66 views

Possible reasons for irregularly high query execution time?

The above is a graph showing the average response times per second (including error bars) for an experiment where I simulate 30 clients which are all invoking the same query multiple times. I ran ...
0
votes
0answers
38 views

Are A or D series VMs better for deploying PostgreSQL on Azure?

In Azure there are VMs that have local storage either as spinning disk (A-series) or SSD (D-series). Considering this space is wiped on reboot... Is there a benefit to choosing the SSD option for ...
1
vote
1answer
47 views

How do I use pg_dump and pg_restore to move a large database to another machine?

I'm a bit unclear on how to use the pg_dump/pg_restore duo to move a large-ish database. Here is the command I use to dump the database (the host and username are taken from environmental variables): ...
1
vote
2answers
45 views

Group by range of years

I've got a big table (~9M rows) and want to group the rows on a field containing the year. So far that's pretty easy: // greatly simplified: SELECT count(*), year FROM dataset GROUP BY year ORDER BY ...
0
votes
0answers
34 views

PostgreSQL: PANIC: heap2_redo: unknown op code 32

I was doing migrations while the server was still accessing the slave DB. I have a master / slave setup. After I restarted the server, I realized I couldn't connect to the SLAVE anymore. I went into ...
0
votes
0answers
43 views

ETL - Moving data from Postgres/Oracle to a TripleStore (RDF)

I'm looking for pointers on how to handle an ETL process that I have to implement for my organization. I know how to query SQL database but i'm not SQL DB specialist. I work more in the sphere of the ...
0
votes
0answers
44 views

Unique index on columns which are allowed to be NULL

I'm having a little problem right now, we use this table in our database: CREATE TABLE offer ( offer_id serial PRIMARY KEY , product_id int NOT NULL REFERENCES product , price_old ...
5
votes
2answers
148 views

Managing CTE execution order under uncertainty

I am writing a large, multi-step CTE for performance reasons. In one query, data must be moved from one table to another, but the quantity of rows moved is uncertain and could be zero. In a ...
5
votes
1answer
521 views

What fillfactor for caching table?

I have heavily updated / accessed table where I store serialized java objects. They are in the table for 2-3 hours (also are being updated during that period) and then removed. Size of table is around ...
2
votes
2answers
33 views

Get all (non repeated) distribuidores with their paises given a producto_solicitud

I have this schema: And as title says I need to get all records from fabricante_distribuidor by given producto_solicitud.id value. I'm doing in this way: SELECT ...
0
votes
1answer
27 views

Initialize, Start Server and Create Database in Single Script

I am writing a provision script for a dev environment with the following: sudo su - postgres <<EOF cd ~/data pg_ctl -D . initdb pg_ctl -D . -l run.log start createdb mydb pg_ctl -D . stop EOF ...
-1
votes
1answer
40 views

How to update values from bytea to varchar in Greenplum?

I need to convert hexa to values and need to update the values in a varchar field, I have tried: select pg_catalog.decode(column,'hex') The above code converted hexa to values but when I try to ...
5
votes
1answer
71 views

Sort by number of related rows in referencing table

Let there be two tables: Users id [pk] | name --------+--------- 1 | Alice 2 | Bob 3 | Charlie 4 | Dan Emails id | user_id | email ----+---------+------- 1 | 1 ...
0
votes
1answer
21 views

create insertion rule on view returning id

I have a table private.products and a view public.products representing that table. And I want to create entries in private.products while inserting into view, it all works right, except that I also ...
0
votes
0answers
56 views

How to Insert records from remote database to local database using dblink in postgresql 9.3

I have a scenario like i have a two DB, one resides in remote server and other resides local. Now i have to fetch the records from remote DB when new records are inserted on tables (in remote DB) and ...
0
votes
1answer
209 views

Error: /var/lib/postgresql/9.3/main is not accessible or does not exist

I have a PostgreSQL db that was running on my server. I tried to do a db_dump and got a weird error message. I eventually thought I would just restart PostgreSQL. However its now stopped and won't ...
1
vote
1answer
32 views

What are the side-effects of disabling nested loops in postgres?

A query of multiple joins spends a lot of time on nested loops. I disabled the nested loops and the query ran much faster. However, I have been told that nested loops might give me wrong results by ...
3
votes
2answers
34 views

How can I determine if a table exists in the current search_path with PLPGSQL?

I'm writing a setup script for an application that's an addon for another application, so I want to check if the tables for the other application exist. If not, I want to give the user a useful ...
2
votes
1answer
51 views
0
votes
0answers
15 views

How to do a pgdump with strings encoded?

When I perform a dump with pg_dump tool, with a "flat" sql format, pg_dump create a regular sql file but the restoration with pg_restore fails because the strings are not escaped. For example, single ...
1
vote
1answer
52 views

Migrate SQL Server binary datadump to postgresql

I just got a very big dataset (+/-55GB) in a binary SQL Server format. Is there an easy way to import this file into a Postgresql Server? I found some converter-programs, but they 'only' convert ...
1
vote
2answers
60 views

Add function parameter to SQL query WHERE clause

I have a web application in java and it uses a query. I don't want to write the query into Java, so I made a function: CREATE OR REPLACE FUNCTION testFunc(inputs text) RETURNS TABLE(...) AS $$ ...
0
votes
0answers
36 views

Translate psql meta-command to SQL

How can I translate a psql meta-command (like \dt or \ds) to the equivalent SQL query? I found some of the translations here. But it would be nice to have a command to do it automatically.
-1
votes
0answers
24 views

Backing up AWS database to an on premise server

I have 2 questions - 1) Are there tools, AWS provided or otherwise, which can continuously backup a cloud-based database (Postgresql RDS) to an on-premise server ? 2) I want to do this, so that I ...
0
votes
0answers
37 views

Getting wrong results from fulltext search in PostgreSQL

This is the query which I am running. The keyword "exhausted" is present only in one of the rows but I am getting all 3 rows. How to avoid the rows where the keyword is not present? DDL: CREATE ...
0
votes
1answer
30 views

Can I use `on delete set null` on a compound foreign key which contains a primary key column?

The docs say: Restricting and cascading deletes are the two most common options. RESTRICT prevents deletion of a referenced row. NO ACTION means that if any referencing rows still exist when the ...
1
vote
1answer
78 views

Slow max, min query in Postgresql View

I have a view and it's a left join between two tables (table_a has hundreds of millions of rows, table_b has ~2 millions). The query SELECT MIN("id") AS "min_id",MAX("id") AS "max_id" FROM "the_view" ...
0
votes
1answer
46 views

Slow Postgres updates if OTHER columns are indexed?

Certain updates take far too long on large Postgres tables. Given these conditions: only one column is being updated, and it is non-indexed the column already has data in it for every row due to a ...
0
votes
1answer
13 views

Adding hstore entries to an uninitialized column

I got bitten by this 'feature' recently. If your hstore column is uninitialized and you start adding entries to it, they are all silently swallowed without error. Is this expected? create table ...
2
votes
1answer
42 views

Dropped an index and recreated it in PostgreSQL 9.2, not used anymore

I have a table with 15M rows, with two indexes; one of them is a very simple BTREE on a string column. While trying to optimize some queries, I created a new partial index on the same column. Using ...