PostgreSQL copy/transfer data from one database to another

Question

I need to copy data from one table to another. the two tables have almost the same structure, but are in different databases.

i tried

INSERT INTO db1.public.table2(
  id,
  name,
  adress,
  lat,
  lng
)
SELECT
  id,
  name,
  adress,
  lat
  lng
FROM db2.public.table2;

wenn i try this, i get error cross database ... not implemented

Answer 1

This is a really straightforward task. Just use dblink for this purpose:

INSERT INTO t(a, b, c)
SELECT a, b, c FROM dblink('host=xxx user=xxx password=xxx dbname=xxx', 'SELECT a, b, c FROM t') AS x(a integer, b integer, c integer)

If you need to fetch data from external database on a regular basis, it would be wise to define a server and user mapping. Then, you could use shorter statement:

dblink('yourdbname', 'your query')

Answer 2

There's also another way to do it. If dblink extension is not available, it's possible to copy data directly in command line, using pipe connecting standard input and ouput:

psql source_database -c 'COPY table TO stdout' | psql target_database -c 'COPY table FROM stdin'

But this is gonna work only in postgres 9.4 or higher

Answer 3

If you are on postgresql 9.0 or later (and probably 8.0 or later) in a psql session you can also use:

CREATE DATABASE new_database TEMPLATE original_database;

The new_database will be a clone of original_database including tables, table schema, encodings, and data.

From the docs:

The principal limitation is that no other sessions can be connected to the source database while it is being copied.

I would recommend that you verify that the clone is in fact correct with judicious selects from the new and old db tables. The docs also say:

It is important to understand, however, that this is not (yet) intended as a general-purpose “COPY DATABASE” facility.