dblink_get_result(3) [centos man page]
DBLINK_GET_RESULT(3) PostgreSQL 9.2.7 Documentation DBLINK_GET_RESULT(3) NAME
dblink_get_result - gets an async query result SYNOPSIS
dblink_get_result(text connname [, bool fail_on_error]) returns setof record DESCRIPTION
dblink_get_result collects the results of an asynchronous query previously sent with dblink_send_query. If the query is not already completed, dblink_get_result will wait until it is. ARGUMENTS
conname Name of the connection to use. fail_on_error If true (the default when omitted) then an error thrown on the remote side of the connection causes an error to also be thrown locally. If false, the remote error is locally reported as a NOTICE, and the function returns no rows. RETURN VALUE
For an async query (that is, a SQL statement returning rows), the function returns the row(s) produced by the query. To use this function, you will need to specify the expected set of columns, as previously discussed for dblink. For an async command (that is, a SQL statement not returning rows), the function returns a single row with a single text column containing the command's status string. It is still necessary to specify that the result will have a single text column in the calling FROM clause. NOTES
This function must be called if dblink_send_query returned 1. It must be called once for each query sent, and one additional time to obtain an empty set result, before the connection can be used again. When using dblink_send_query and dblink_get_result, dblink fetches the entire remote query result before returning any of it to the local query processor. If the query returns a large number of rows, this can result in transient memory bloat in the local session. It may be better to open such a query as a cursor with dblink_open and then fetch a manageable number of rows at a time. Alternatively, use plain dblink(), which avoids memory bloat by spooling large result sets to disk. EXAMPLES
contrib_regression=# SELECT dblink_connect('dtest1', 'dbname=contrib_regression'); dblink_connect ---------------- OK (1 row) contrib_regression=# SELECT * FROM contrib_regression-# dblink_send_query('dtest1', 'select * from foo where f1 < 3') AS t1; t1 ---- 1 (1 row) contrib_regression=# SELECT * FROM dblink_get_result('dtest1') AS t1(f1 int, f2 text, f3 text[]); f1 | f2 | f3 ----+----+------------ 0 | a | {a0,b0,c0} 1 | b | {a1,b1,c1} 2 | c | {a2,b2,c2} (3 rows) contrib_regression=# SELECT * FROM dblink_get_result('dtest1') AS t1(f1 int, f2 text, f3 text[]); f1 | f2 | f3 ----+----+---- (0 rows) contrib_regression=# SELECT * FROM contrib_regression-# dblink_send_query('dtest1', 'select * from foo where f1 < 3; select * from foo where f1 > 6') AS t1; t1 ---- 1 (1 row) contrib_regression=# SELECT * FROM dblink_get_result('dtest1') AS t1(f1 int, f2 text, f3 text[]); f1 | f2 | f3 ----+----+------------ 0 | a | {a0,b0,c0} 1 | b | {a1,b1,c1} 2 | c | {a2,b2,c2} (3 rows) contrib_regression=# SELECT * FROM dblink_get_result('dtest1') AS t1(f1 int, f2 text, f3 text[]); f1 | f2 | f3 ----+----+--------------- 7 | h | {a7,b7,c7} 8 | i | {a8,b8,c8} 9 | j | {a9,b9,c9} 10 | k | {a10,b10,c10} (4 rows) contrib_regression=# SELECT * FROM dblink_get_result('dtest1') AS t1(f1 int, f2 text, f3 text[]); f1 | f2 | f3 ----+----+---- (0 rows) PostgreSQL 9.2.7 2014-02-17 DBLINK_GET_RESULT(3)
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DELETE(7) PostgreSQL 9.2.7 Documentation DELETE(7) NAME
DELETE - delete rows of a table SYNOPSIS
[ WITH [ RECURSIVE ] with_query [, ...] ] DELETE FROM [ ONLY ] table_name [ * ] [ [ AS ] alias ] [ USING using_list ] [ WHERE condition | WHERE CURRENT OF cursor_name ] [ RETURNING * | output_expression [ [ AS ] output_name ] [, ...] ] DESCRIPTION
DELETE deletes rows that satisfy the WHERE clause from the specified table. If the WHERE clause is absent, the effect is to delete all rows in the table. The result is a valid, but empty table. Tip TRUNCATE(7) is a PostgreSQL extension that provides a faster mechanism to remove all rows from a table. There are two ways to delete rows in a table using information contained in other tables in the database: using sub-selects, or specifying additional tables in the USING clause. Which technique is more appropriate depends on the specific circumstances. The optional RETURNING clause causes DELETE to compute and return value(s) based on each row actually deleted. Any expression using the table's columns, and/or columns of other tables mentioned in USING, can be computed. The syntax of the RETURNING list is identical to that of the output list of SELECT. You must have the DELETE privilege on the table to delete from it, as well as the SELECT privilege for any table in the USING clause or whose values are read in the condition. PARAMETERS
with_query The WITH clause allows you to specify one or more subqueries that can be referenced by name in the DELETE query. See Section 7.8, "WITH Queries (Common Table Expressions)", in the documentation and SELECT(7) for details. table_name The name (optionally schema-qualified) of the table to delete rows from. If ONLY is specified before the table name, matching rows are deleted from the named table only. If ONLY is not specified, matching rows are also deleted from any tables inheriting from the named table. Optionally, * can be specified after the table name to explicitly indicate that descendant tables are included. alias A substitute name for the target table. When an alias is provided, it completely hides the actual name of the table. For example, given DELETE FROM foo AS f, the remainder of the DELETE statement must refer to this table as f not foo. using_list A list of table expressions, allowing columns from other tables to appear in the WHERE condition. This is similar to the list of tables that can be specified in the FROM Clause of a SELECT statement; for example, an alias for the table name can be specified. Do not repeat the target table in the using_list, unless you wish to set up a self-join. condition An expression that returns a value of type boolean. Only rows for which this expression returns true will be deleted. cursor_name The name of the cursor to use in a WHERE CURRENT OF condition. The row to be deleted is the one most recently fetched from this cursor. The cursor must be a non-grouping query on the DELETE's target table. Note that WHERE CURRENT OF cannot be specified together with a Boolean condition. See DECLARE(7) for more information about using cursors with WHERE CURRENT OF. output_expression An expression to be computed and returned by the DELETE command after each row is deleted. The expression can use any column names of the table named by table_name or table(s) listed in USING. Write * to return all columns. output_name A name to use for a returned column. OUTPUTS
On successful completion, a DELETE command returns a command tag of the form DELETE count The count is the number of rows deleted. Note that the number may be less than the number of rows that matched the condition when deletes were suppressed by a BEFORE DELETE trigger. If count is 0, no rows were deleted by the query (this is not considered an error). If the DELETE command contains a RETURNING clause, the result will be similar to that of a SELECT statement containing the columns and values defined in the RETURNING list, computed over the row(s) deleted by the command. NOTES
PostgreSQL lets you reference columns of other tables in the WHERE condition by specifying the other tables in the USING clause. For example, to delete all films produced by a given producer, one can do: DELETE FROM films USING producers WHERE producer_id = producers.id AND producers.name = 'foo'; What is essentially happening here is a join between films and producers, with all successfully joined films rows being marked for deletion. This syntax is not standard. A more standard way to do it is: DELETE FROM films WHERE producer_id IN (SELECT id FROM producers WHERE name = 'foo'); In some cases the join style is easier to write or faster to execute than the sub-select style. EXAMPLES
Delete all films but musicals: DELETE FROM films WHERE kind <> 'Musical'; Clear the table films: DELETE FROM films; Delete completed tasks, returning full details of the deleted rows: DELETE FROM tasks WHERE status = 'DONE' RETURNING *; Delete the row of tasks on which the cursor c_tasks is currently positioned: DELETE FROM tasks WHERE CURRENT OF c_tasks; COMPATIBILITY
This command conforms to the SQL standard, except that the USING and RETURNING clauses are PostgreSQL extensions, as is the ability to use WITH with DELETE. PostgreSQL 9.2.7 2014-02-17 DELETE(7)