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243 lines
6.1 KiB
Plaintext
243 lines
6.1 KiB
Plaintext
==================================================================
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Name
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dblink -- Returns a set from a remote database
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Synopsis
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dblink(text connstr, text sql [, bool fail_on_error])
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dblink(text connname, text sql [, bool fail_on_error])
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dblink(text sql [, bool fail_on_error])
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Inputs
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connname
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connstr
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If two arguments are present, the first is first assumed to be a specific
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connection name to use. If the name is not found, the argument is then
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assumed to be a valid connection string, of standard libpq format,
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e.g.: "hostaddr=127.0.0.1 dbname=mydb user=postgres password=mypasswd"
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If only one argument is used, then the unnamed connection is used.
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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 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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select * from dblink('dbname=postgres','select proname, prosrc from pg_proc')
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as t1(proname name, prosrc text) where proname like 'bytea%';
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proname | prosrc
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------------+------------
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byteacat | byteacat
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byteaeq | byteaeq
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bytealt | bytealt
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byteale | byteale
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byteagt | byteagt
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byteage | byteage
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byteane | byteane
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byteacmp | byteacmp
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bytealike | bytealike
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byteanlike | byteanlike
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byteain | byteain
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byteaout | byteaout
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(12 rows)
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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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select * from dblink('select proname, prosrc from pg_proc')
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as t1(proname name, prosrc text) where proname like 'bytea%';
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proname | prosrc
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------------+------------
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byteacat | byteacat
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byteaeq | byteaeq
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bytealt | bytealt
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byteale | byteale
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byteagt | byteagt
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byteage | byteage
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byteane | byteane
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byteacmp | byteacmp
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bytealike | bytealike
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byteanlike | byteanlike
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byteain | byteain
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byteaout | byteaout
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(12 rows)
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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 * from dblink('myconn','select proname, prosrc from pg_proc')
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as t1(proname name, prosrc text) where proname like 'bytea%';
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proname | prosrc
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------------+------------
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bytearecv | bytearecv
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byteasend | byteasend
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byteale | byteale
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byteagt | byteagt
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byteage | byteage
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byteane | byteane
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byteacmp | byteacmp
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bytealike | bytealike
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byteanlike | byteanlike
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byteacat | byteacat
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byteaeq | byteaeq
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bytealt | bytealt
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byteain | byteain
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byteaout | byteaout
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(14 rows)
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==================================================================
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A more convenient way to use dblink may be to create a view:
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create view myremote_pg_proc as
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select *
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from dblink('dbname=postgres','select proname, prosrc from pg_proc')
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as t1(proname name, prosrc text);
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Then you can simply write:
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select * from myremote_pg_proc where proname like 'bytea%';
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==================================================================
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Name
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dblink_send_query -- Sends an async query to a remote database
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Synopsis
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dblink_send_query(text connname, text sql)
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Inputs
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connname
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The specific connection name to use.
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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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Outputs
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Returns int. A return value of 1 if the query was successfully dispatched,
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0 otherwise. If 1, results must be fetched by dblink_get_result(connname).
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A running query may be cancelled by dblink_cancel_query(connname).
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Example usage
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SELECT dblink_connect('dtest1', 'dbname=contrib_regression');
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SELECT * from
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dblink_send_query('dtest1', 'select * from foo where f1 < 3') as t1;
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==================================================================
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Name
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dblink_get_result -- Gets an async query result
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Synopsis
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dblink_get_result(text connname [, bool fail_on_error])
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Inputs
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connname
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The specific connection name to use. An asynchronous query must
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have already been sent using dblink_send_query()
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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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Notes
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Blocks until a result gets available.
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This function *must* be called if dblink_send_query returned
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a 1, even on cancelled queries - otherwise the connection
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can't be used anymore. It must be called once for each query
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sent, and one additional time to obtain an empty set result,
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prior to using the connection again.
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Example usage
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contrib_regression=# SELECT dblink_connect('dtest1', 'dbname=contrib_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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contrib_regression=# SELECT * from
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contrib_regression-# dblink_send_query('dtest1', 'select * from foo where f1 < 3') as t1;
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t1
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----
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1
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(1 row)
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contrib_regression=# SELECT * from dblink_get_result('dtest1') as t1(f1 int, f2 text, f3 text[]);
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f1 | f2 | f3
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----+----+------------
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0 | a | {a0,b0,c0}
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1 | b | {a1,b1,c1}
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2 | c | {a2,b2,c2}
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(3 rows)
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contrib_regression=# SELECT * from dblink_get_result('dtest1') as t1(f1 int, f2 text, f3 text[]);
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f1 | f2 | f3
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----+----+----
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(0 rows)
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contrib_regression=# SELECT * from
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dblink_send_query('dtest1', 'select * from foo where f1 < 3; select * from foo where f1 > 6') as t1;
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t1
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----
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1
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(1 row)
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contrib_regression=# SELECT * from dblink_get_result('dtest1') as t1(f1 int, f2 text, f3 text[]);
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f1 | f2 | f3
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----+----+------------
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0 | a | {a0,b0,c0}
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1 | b | {a1,b1,c1}
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2 | c | {a2,b2,c2}
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(3 rows)
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contrib_regression=# SELECT * from dblink_get_result('dtest1') as t1(f1 int, f2 text, f3 text[]);
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f1 | f2 | f3
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----+----+---------------
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7 | h | {a7,b7,c7}
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8 | i | {a8,b8,c8}
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9 | j | {a9,b9,c9}
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10 | k | {a10,b10,c10}
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(4 rows)
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contrib_regression=# SELECT * from dblink_get_result('dtest1') as t1(f1 int, f2 text, f3 text[]);
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f1 | f2 | f3
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----+----+----
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(0 rows)
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