postgresql/contrib/dblink/doc/misc
Joe Conway 52a3ed9fac Added async query capability. Original patch by
Kai Londenberg, modified by Joe Conway
2006-09-02 21:11:15 +00:00

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$PostgreSQL: pgsql/contrib/dblink/doc/misc,v 1.4 2006/09/02 21:11:15 joe Exp $
==================================================================
Name
dblink_current_query -- returns the current query string
Synopsis
dblink_current_query () RETURNS text
Inputs
None
Outputs
Returns text -- a copy of the currently executing query
Example usage
test=# select dblink_current_query() from (select dblink('dbname=postgres','select oid, proname from pg_proc where proname = ''byteacat''') as f1) as t1;
dblink_current_query
-----------------------------------------------------------------------------------------------------------------------------------------------------
select dblink_current_query() from (select dblink('dbname=postgres','select oid, proname from pg_proc where proname = ''byteacat''') as f1) as t1;
(1 row)
==================================================================
Name
dblink_get_pkey -- returns the position and field names of a relation's
primary key fields
Synopsis
dblink_get_pkey(text relname) RETURNS setof dblink_pkey_results
Inputs
relname
any relation name;
e.g. 'foobar'
Outputs
Returns setof dblink_pkey_results -- one row for each primary key field,
in order of position in the key. dblink_pkey_results is defined as follows:
CREATE TYPE dblink_pkey_results AS (position int4, colname text);
Example usage
test=# select * from dblink_get_pkey('foobar');
position | colname
----------+---------
1 | f1
2 | f2
3 | f3
4 | f4
5 | f5
==================================================================
Name
dblink_build_sql_insert -- builds an insert statement using a local
tuple, replacing the selection key field
values with alternate supplied values
dblink_build_sql_delete -- builds a delete statement using supplied
values for selection key field values
dblink_build_sql_update -- builds an update statement using a local
tuple, replacing the selection key field
values with alternate supplied values
Synopsis
dblink_build_sql_insert(text relname
,int2vector primary_key_attnums
,int2 num_primary_key_atts
,_text src_pk_att_vals_array
,_text tgt_pk_att_vals_array) RETURNS text
dblink_build_sql_delete(text relname
,int2vector primary_key_attnums
,int2 num_primary_key_atts
,_text tgt_pk_att_vals_array) RETURNS text
dblink_build_sql_update(text relname
,int2vector primary_key_attnums
,int2 num_primary_key_atts
,_text src_pk_att_vals_array
,_text tgt_pk_att_vals_array) RETURNS text
Inputs
relname
any relation name;
e.g. 'foobar'
primary_key_attnums
vector of primary key attnums (1 based, see pg_index.indkey);
e.g. '1 2'
num_primary_key_atts
number of primary key attnums in the vector; e.g. 2
src_pk_att_vals_array
array of primary key values, used to look up the local matching
tuple, the values of which are then used to construct the SQL
statement
tgt_pk_att_vals_array
array of primary key values, used to replace the local tuple
values in the SQL statement
Outputs
Returns text -- requested SQL statement
Example usage
test=# select dblink_build_sql_insert('foo','1 2',2,'{"1", "a"}','{"1", "b''a"}');
dblink_build_sql_insert
--------------------------------------------------
INSERT INTO foo(f1,f2,f3) VALUES('1','b''a','1')
(1 row)
test=# select dblink_build_sql_delete('MyFoo','1 2',2,'{"1", "b"}');
dblink_build_sql_delete
---------------------------------------------
DELETE FROM "MyFoo" WHERE f1='1' AND f2='b'
(1 row)
test=# select dblink_build_sql_update('foo','1 2',2,'{"1", "a"}','{"1", "b"}');
dblink_build_sql_update
-------------------------------------------------------------
UPDATE foo SET f1='1',f2='b',f3='1' WHERE f1='1' AND f2='b'
(1 row)
==================================================================
Name
dblink_get_connections -- returns a text array of all active named
dblink connections
Synopsis
dblink_get_connections() RETURNS text[]
Inputs
none
Outputs
Returns text array of all active named dblink connections
Example usage
SELECT dblink_get_connections();
==================================================================
Name
dblink_is_busy -- checks to see if named connection is busy
with an async query
Synopsis
dblink_is_busy(text connname) RETURNS int
Inputs
connname
The specific connection name to use.
Outputs
Returns 1 if connection is busy, 0 if it is not busy.
If this function returns 0, it is guaranteed that dblink_get_result
will not block.
Example usage
SELECT dblink_is_busy('dtest1');
==================================================================
Name
dblink_cancel_query -- cancels any active query on the named connection
Synopsis
dblink_cancel_query(text connname) RETURNS text
Inputs
connname
The specific connection name to use.
Outputs
Returns "OK" on success, or an error message on failure.
Example usage
SELECT dblink_cancel_query('dtest1');
==================================================================
Name
dblink_error_message -- gets last error message on the named connection
Synopsis
dblink_error_message(text connname) RETURNS text
Inputs
connname
The specific connection name to use.
Outputs
Returns last error message.
Example usage
SELECT dblink_error_message('dtest1');