pg_prepare(3) [php man page]
PG_PREPARE(3) PG_PREPARE(3) pg_prepare - Submits a request to create a prepared statement with the given parameters, and waits for completion. SYNOPSIS
resource pg_prepare ([resource $connection], string $stmtname, string $query) DESCRIPTION
pg_prepare(3) creates a prepared statement for later execution with pg_execute(3) or pg_send_execute(3). This feature allows commands that will be used repeatedly to be parsed and planned just once, rather than each time they are executed. pg_prepare(3) is supported only against PostgreSQL 7.4 or higher connections; it will fail when using earlier versions. The function creates a prepared statement named $stmtname from the $query string, which must contain a single SQL command. $stmtname may be "" to create an unnamed statement, in which case any pre-existing unnamed statement is automatically replaced; otherwise it is an error if the statement name is already defined in the current session. If any parameters are used, they are referred to in the $query as $1, $2, etc. Prepared statements for use with pg_prepare(3) can also be created by executing SQL PREPARE statements. (But pg_prepare(3) is more flexi- ble since it does not require parameter types to be pre-specified.) Also, although there is no PHP function for deleting a prepared state- ment, the SQL DEALLOCATE statement can be used for that purpose. PARAMETERS
o $connection - PostgreSQL database connection resource. When $connection is not present, the default connection is used. The default connection is the last connection made by pg_connect(3) or pg_pconnect(3). o $stmtname - The name to give the prepared statement. Must be unique per-connection. If "" is specified, then an unnamed statement is cre- ated, overwriting any previously defined unnamed statement. o $query - The parameterized SQL statement. Must contain only a single statement. (multiple statements separated by semi-colons are not allowed.) If any parameters are used, they are referred to as $1, $2, etc. RETURN VALUES
A query result resource on success or FALSE on failure. EXAMPLES
Example #1 Using pg_prepare(3) <?php // Connect to a database named "mary" $dbconn = pg_connect("dbname=mary"); // Prepare a query for execution $result = pg_prepare($dbconn, "my_query", 'SELECT * FROM shops WHERE name = $1'); // Execute the prepared query. Note that it is not necessary to escape // the string "Joe's Widgets" in any way $result = pg_execute($dbconn, "my_query", array("Joe's Widgets")); // Execute the same prepared query, this time with a different parameter $result = pg_execute($dbconn, "my_query", array("Clothes Clothes Clothes")); ?> SEE ALSO
pg_execute(3), pg_send_execute(3). PHP Documentation Group PG_PREPARE(3)
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PREPARE(7) SQL Commands PREPARE(7) NAME
PREPARE - prepare a statement for execution SYNOPSIS
PREPARE name [ ( datatype [, ...] ) ] AS statement DESCRIPTION
PREPARE creates a prepared statement. A prepared statement is a server-side object that can be used to optimize performance. When the PRE- PARE statement is executed, the specified statement is parsed, rewritten, and planned. When an EXECUTE command is subsequently issued, the prepared statement need only be executed. Thus, the parsing, rewriting, and planning stages are only performed once, instead of every time the statement is executed. Prepared statements can take parameters: values that are substituted into the statement when it is executed. When creating the prepared statement, refer to parameters by position, using $1, $2, etc. A corresponding list of parameter data types can optionally be specified. When a parameter's data type is not specified or is declared as unknown, the type is inferred from the context in which the parameter is used (if possible). When executing the statement, specify the actual values for these parameters in the EXECUTE statement. Refer to EXECUTE [execute(7)] for more information about that. Prepared statements only last for the duration of the current database session. When the session ends, the prepared statement is forgotten, so it must be recreated before being used again. This also means that a single prepared statement cannot be used by multiple simultaneous database clients; however, each client can create their own prepared statement to use. The prepared statement can be manually cleaned up using the DEALLOCATE [deallocate(7)] command. Prepared statements have the largest performance advantage when a single session is being used to execute a large number of similar state- ments. The performance difference will be particularly significant if the statements are complex to plan or rewrite, for example, if the query involves a join of many tables or requires the application of several rules. If the statement is relatively simple to plan and re- write but relatively expensive to execute, the performance advantage of prepared statements will be less noticeable. PARAMETERS
name An arbitrary name given to this particular prepared statement. It must be unique within a single session and is subsequently used to execute or deallocate a previously prepared statement. datatype The data type of a parameter to the prepared statement. If the data type of a particular parameter is unspecified or is specified as unknown, it will be inferred from the context in which the parameter is used. To refer to the parameters in the prepared statement itself, use $1, $2, etc. statement Any SELECT, INSERT, UPDATE, DELETE, or VALUES statement. NOTES
In some situations, the query plan produced for a prepared statement will be inferior to the query plan that would have been chosen if the statement had been submitted and executed normally. This is because when the statement is planned and the planner attempts to determine the optimal query plan, the actual values of any parameters specified in the statement are unavailable. PostgreSQL collects statistics on the distribution of data in the table, and can use constant values in a statement to make guesses about the likely result of executing the statement. Since this data is unavailable when planning prepared statements with parameters, the chosen plan might be suboptimal. To exam- ine the query plan PostgreSQL has chosen for a prepared statement, use EXPLAIN [explain(7)]. For more information on query planning and the statistics collected by PostgreSQL for that purpose, see the ANALYZE [analyze(7)] documenta- tion. You can see all available prepared statements of a session by querying the pg_prepared_statements system view. EXAMPLES
Create a prepared statement for an INSERT statement, and then execute it: PREPARE fooplan (int, text, bool, numeric) AS INSERT INTO foo VALUES($1, $2, $3, $4); EXECUTE fooplan(1, 'Hunter Valley', 't', 200.00); Create a prepared statement for a SELECT statement, and then execute it: PREPARE usrrptplan (int) AS SELECT * FROM users u, logs l WHERE u.usrid=$1 AND u.usrid=l.usrid AND l.date = $2; EXECUTE usrrptplan(1, current_date); Note that the data type of the second parameter is not specified, so it is inferred from the context in which $2 is used. COMPATIBILITY
The SQL standard includes a PREPARE statement, but it is only for use in embedded SQL. This version of the PREPARE statement also uses a somewhat different syntax. SEE ALSO
DEALLOCATE [deallocate(7)], EXECUTE [execute(7)] SQL - Language Statements 2010-05-14 PREPARE(7)