116 lines
4.4 KiB
Markdown
116 lines
4.4 KiB
Markdown
---
|
|
layout: default_docs
|
|
title: Chapter 6. Calling Stored Functions
|
|
header: Chapter 6. Calling Stored Functions
|
|
resource: media
|
|
previoustitle: Creating and Modifying Database Objects
|
|
previous: ddl.html
|
|
nexttitle: Chapter 7. Storing Binary Data
|
|
next: binary-data.html
|
|
---
|
|
|
|
**Table of Contents**
|
|
|
|
* [Obtaining a `ResultSet` from a stored function](callproc.html#callproc-resultset)
|
|
* [From a Function Returning `SETOF` type](callproc.html#callproc-resultset-setof)
|
|
* [From a Function Returning a refcursor](callproc.html#callproc-resultset-refcursor)
|
|
|
|
<a name="call-function-example"></a>
|
|
**Example 6.1. Calling a built in stored function**
|
|
|
|
This example shows how to call a PostgreSQL™ built in function, `upper`, which
|
|
simply converts the supplied string argument to uppercase.
|
|
|
|
`CallableStatement upperProc = conn.prepareCall("{ ? = call upper( ? ) }");`
|
|
`upperProc.registerOutParameter(1, Types.VARCHAR);`
|
|
`upperProc.setString(2, "lowercase to uppercase");`
|
|
`upperProc.execute();`
|
|
`String upperCased = upperProc.getString(1);`
|
|
`upperProc.close();`
|
|
|
|
<a name="callproc-resultset"></a>
|
|
# Obtaining a `ResultSet` from a stored function
|
|
|
|
PostgreSQL's™ stored functions can return results in two different ways. The
|
|
function may return either a refcursor value or a `SETOF` some datatype. Depending
|
|
on which of these return methods are used determines how the function should be
|
|
called.
|
|
|
|
<a name="callproc-resultset-setof"></a>
|
|
## From a Function Returning `SETOF` type
|
|
|
|
Functions that return data as a set should not be called via the `CallableStatement`
|
|
interface, but instead should use the normal `Statement` or `PreparedStatement`
|
|
interfaces.
|
|
|
|
<a name="setof-resultset"></a>
|
|
**Example 6.2. Getting `SETOF` type values from a function**
|
|
|
|
`Statement stmt = conn.createStatement();`
|
|
`stmt.execute("CREATE OR REPLACE FUNCTION setoffunc() RETURNS SETOF int AS "`
|
|
`+ "' SELECT 1 UNION SELECT 2;' LANGUAGE sql");`
|
|
`ResultSet rs = stmt.executeQuery("SELECT * FROM setoffunc()");`
|
|
`while (rs.next())`
|
|
`{`
|
|
`// do something`
|
|
`}`
|
|
`rs.close();`
|
|
`stmt.close();`
|
|
|
|
<a name="callproc-resultset-refcursor"></a>
|
|
## From a Function Returning a refcursor
|
|
|
|
When calling a function that returns a refcursor you must cast the return type of
|
|
`getObject` to a `ResultSet`
|
|
|
|
### Note
|
|
|
|
> One notable limitation of the current support for a `ResultSet` created from
|
|
a refcursor is that even though it is a cursor backed `ResultSet`, all data will
|
|
be retrieved and cached on the client. The `Statement` fetch size parameter
|
|
described in the section called [“Getting results based on a cursor”](query.html#query-with-cursor)
|
|
is ignored. This limitation is a deficiency of the JDBC driver, not the server,
|
|
and it is technically possible to remove it, we just haven't found the time.
|
|
|
|
<a name="get-refcursor-from-function-call"></a>
|
|
**Example 6.3. Getting refcursor Value From a Function**
|
|
|
|
`// Setup function to call.`
|
|
`Statement stmt = conn.createStatement();`
|
|
`stmt.execute("CREATE OR REPLACE FUNCTION refcursorfunc() RETURNS refcursor AS '"`
|
|
`+ " DECLARE "`
|
|
`+ " mycurs refcursor; "`
|
|
`+ " BEGIN "`
|
|
`+ " OPEN mycurs FOR SELECT 1 UNION SELECT 2; "`
|
|
`+ " RETURN mycurs; "`
|
|
`+ " END;' language plpgsql");`
|
|
`stmt.close();`<br />
|
|
|
|
`// We must be inside a transaction for cursors to work.`
|
|
`conn.setAutoCommit(false);`<br />
|
|
|
|
`// Procedure call.`
|
|
`CallableStatement proc = conn.prepareCall("{ ? = call refcursorfunc() }");`
|
|
`proc.registerOutParameter(1, Types.OTHER);`
|
|
`proc.execute();`
|
|
`ResultSet results = (ResultSet) proc.getObject(1);`
|
|
`while (results.next())`
|
|
`{`
|
|
`// do something with the results.`
|
|
`}`
|
|
`results.close();`
|
|
`proc.close();`
|
|
|
|
It is also possible to treat the refcursor return value as a cursor name directly.
|
|
To do this, use the `getString` of `ResultSet`. With the underlying cursor name,
|
|
you are free to directly use cursor commands on it, such as `FETCH` and `MOVE`.
|
|
|
|
<a name="refcursor-string-example"></a>
|
|
**Example 6.4. Treating refcursor as a cursor name**
|
|
|
|
`conn.setAutoCommit(false);`
|
|
`CallableStatement proc = conn.prepareCall("{ ? = call refcursorfunc() }");`
|
|
`proc.registerOutParameter(1, Types.OTHER);`
|
|
`proc.execute();`
|
|
`String cursorName = proc.getString(1);`
|
|
`proc.close();` |