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6f7fc0bade
unlike template0 and template1 does not have any special status in terms of backend functionality. However, all external utilities such as createuser and createdb now connect to "postgres" instead of template1, and the documentation is changed to encourage people to use "postgres" instead of template1 as a play area. This should fix some longstanding gotchas involving unexpected propagation of database objects by createdb (when you used template1 without understanding the implications), as well as ameliorating the problem that CREATE DATABASE is unhappy if anyone else is connected to template1. Patch by Dave Page, minor editing by Tom Lane. All per recent pghackers discussions.
213 lines
4.9 KiB
Plaintext
213 lines
4.9 KiB
Plaintext
==================================================================
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Name
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dblink_open -- Opens a cursor on a remote database
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Synopsis
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dblink_open(text cursorname, text sql [, bool fail_on_error])
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dblink_open(text connname, text cursorname, text sql [, bool fail_on_error])
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Inputs
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connname
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if three arguments are present, the first is taken as the specific
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connection name to use; otherwise the unnamed connection is assumed
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cursorname
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a reference name for the cursor
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sql
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sql statement that you wish to execute on the remote host
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e.g. "select * from pg_class"
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fail_on_error
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If true (default when not present) then an ERROR thrown on the remote side
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of the connection causes an ERROR to also be thrown locally. If false, the
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remote ERROR is locally treated as a NOTICE, and the return value is set
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to 'ERROR'.
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Outputs
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Returns status = "OK"
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Note
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1) dblink_connect(text connstr) must be executed first
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2) dblink_open starts an explicit transaction. If, after using dblink_open,
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you use dblink_exec to change data, and then an error occurs or you use
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dblink_disconnect without a dblink_close first, your change *will* be
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lost. Also, using dblink_close explicitly ends the transaction and thus
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effectively closes *all* open cursors.
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Example usage
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test=# select dblink_connect('dbname=postgres');
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dblink_connect
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----------------
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OK
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(1 row)
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test=# select dblink_open('foo','select proname, prosrc from pg_proc');
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dblink_open
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-------------
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OK
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(1 row)
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==================================================================
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Name
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dblink_fetch -- Returns a set from an open cursor on a remote database
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Synopsis
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dblink_fetch(text cursorname, int32 howmany [, bool fail_on_error])
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dblink_fetch(text connname, text cursorname, int32 howmany [, bool fail_on_error])
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Inputs
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connname
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if three arguments are present, the first is taken as the specific
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connection name to use; otherwise the unnamed connection is assumed
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cursorname
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The reference name for the cursor
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howmany
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Maximum number of rows to retrieve. The next howmany rows are fetched,
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starting at the current cursor position, moving forward. Once the cursor
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has positioned to the end, no more rows are produced.
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fail_on_error
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If true (default when not present) then an ERROR thrown on the remote side
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of the connection causes an ERROR to also be thrown locally. If false, the
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remote ERROR is locally treated as a NOTICE, and no rows are returned.
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Outputs
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Returns setof record
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Example usage
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test=# select dblink_connect('dbname=postgres');
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dblink_connect
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----------------
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OK
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(1 row)
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test=# select dblink_open('foo','select proname, prosrc from pg_proc where proname like ''bytea%''');
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dblink_open
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-------------
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OK
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(1 row)
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test=# select * from dblink_fetch('foo',5) as (funcname name, source text);
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funcname | source
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----------+----------
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byteacat | byteacat
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byteacmp | byteacmp
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byteaeq | byteaeq
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byteage | byteage
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byteagt | byteagt
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(5 rows)
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test=# select * from dblink_fetch('foo',5) as (funcname name, source text);
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funcname | source
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-----------+-----------
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byteain | byteain
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byteale | byteale
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bytealike | bytealike
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bytealt | bytealt
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byteane | byteane
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(5 rows)
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test=# select * from dblink_fetch('foo',5) as (funcname name, source text);
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funcname | source
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------------+------------
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byteanlike | byteanlike
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byteaout | byteaout
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(2 rows)
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test=# select * from dblink_fetch('foo',5) as (funcname name, source text);
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funcname | source
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----------+--------
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(0 rows)
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==================================================================
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Name
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dblink_close -- Closes a cursor on a remote database
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Synopsis
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dblink_close(text cursorname [, bool fail_on_error])
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dblink_close(text connname, text cursorname [, bool fail_on_error])
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Inputs
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connname
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if two arguments are present, the first is taken as the specific
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connection name to use; otherwise the unnamed connection is assumed
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cursorname
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a reference name for the cursor
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fail_on_error
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If true (default when not present) then an ERROR thrown on the remote side
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of the connection causes an ERROR to also be thrown locally. If false, the
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remote ERROR is locally treated as a NOTICE, and the return value is set
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to 'ERROR'.
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Outputs
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Returns status = "OK"
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Note
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dblink_connect(text connstr) or dblink_connect(text connname, text connstr)
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must be executed first.
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Example usage
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test=# select dblink_connect('dbname=postgres');
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dblink_connect
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----------------
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OK
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(1 row)
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test=# select dblink_open('foo','select proname, prosrc from pg_proc');
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dblink_open
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-------------
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OK
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(1 row)
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test=# select dblink_close('foo');
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dblink_close
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--------------
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OK
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(1 row)
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select dblink_connect('myconn','dbname=regression');
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dblink_connect
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----------------
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OK
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(1 row)
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select dblink_open('myconn','foo','select proname, prosrc from pg_proc');
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dblink_open
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-------------
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OK
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(1 row)
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select dblink_close('myconn','foo');
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dblink_close
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--------------
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OK
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(1 row)
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