internals:pdo:brainstorming

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internals:pdo:brainstorming [2009/12/06 13:30] – more documentation eis_osinternals:pdo:brainstorming [2017/09/22 13:28] (current) – external edit 127.0.0.1
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   * error handling   * error handling
   * nested transaction (emulation)   * nested transaction (emulation)
 +
 +
 +=== Parameter Binding without Preparing ===
 +Allow prepareless binding of parameters for queries, like PostgreSQL PQexecParams.
 +  * queryParam() ?
 +
 +
 +
  
 ===== PDO Binding behaviour (5.3) ===== ===== PDO Binding behaviour (5.3) =====
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 for all bindValue/bindParam/execute input for all bindValue/bindParam/execute input
  
 +
 +=== Why do we need improvements to binding? ===
 +Currently has no standard or agreement how parameters like PDO_PARAM_BOOL should be handled on the user side or the internal PDO drivers.
 +There are even disagreements between PDOs code comment, explaining PDO_PARAM_INT is the internal PHP type, and the manual telling us it's the database native type.
 +The result is there is no agreement how even simple parameters should be bound properly and so each driver does it's own guessing how parameters are handled.
 +
 +=== The current situation ===
 +There are two basic categories how currently driver handle bindings:
 +Trying to guess the right meaning by the zval type (even if PDO is told to use a certain type)
 +Or try to convert it to string and let the database handle most stuff.
 +
 +So each driver needs some special care when binding, generally for PDO mysql you need to cast to the right type as setting the binding type constant has no affect.
 +The PDO core already convert doubles to string in the pdo_stmt.c really_register_bound_param function.
 +The current code may or may not separate the zval, so the contents of the variable may change after a successful binding or executing of a statement.
 +
 +
 +=== Proposal ===
 +PDO should enforce the zval type in really_register_bound_param so drivers will get a pre-filtered parameters
 +
 +This would mean: 
 +PDO_PARAM_* will map to internal PHP types, as the code comments in the enum pdo_param_type already tells us.
 +PDO_PARAM_ZVAL will be introduced to user space to let zvals pass directly.
 +
 +If the zval type isn't right, PDO should do a zval separation before converting so no user space variables will be altered.
 +
 +PDO_PARAM_DOUBLE should be introduced later to complete the current support.
 +
 +
 +=== Problems ===
 +PostgreSQL: Currently it's possible to pass a string like "NO" with PDO::PARAM_BOOL,
 +the string contents will be evaluated by the pdo driver, so "no" gets the equivalent of zend false.
 +
 +As soon as PDO Core enforces types and simply use convert_to_boolean bindValue(':foo', 'NO', PDO::PARAM_BOOL) would result into zend true, passed to pdo postgre it would store true! 
 +
 +But as bindValue defaults to PDO::PARAM_STR and so currently with PostgreSQL you don't need PDO::PARAM_BOOL the impact on current software shouldn't be big.
 +
 +
 +=== Workarounds ===
 +Possible workaround: A special convert_to_boolean function to support SQL FALSE and NO as zend false, however this would be unnatural to PHP core.
 +
 +
 +=== Matrix ===
 | zval/PDO           ^ PDO_PARAM_NULL  ^ PDO_PARAM_BOOL     ^ PDO_PARAM_INT     ^ PDO_PARAM_STR           ^ PDO_PARAM_LOB           ^ PDO_PARAM_AUTO (new)    ^ | zval/PDO           ^ PDO_PARAM_NULL  ^ PDO_PARAM_BOOL     ^ PDO_PARAM_INT     ^ PDO_PARAM_STR           ^ PDO_PARAM_LOB           ^ PDO_PARAM_AUTO (new)    ^
 ^ IS_NULL            | - no convert -  | SQL_NULL           | SQL_NULL          | SQL_NULL                | SQL_NULL                | SQL_NULL                | ^ IS_NULL            | - no convert -  | SQL_NULL           | SQL_NULL          | SQL_NULL                | SQL_NULL                | SQL_NULL                |
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 (3) Allowing streams (3) Allowing streams
  
-For compatibility the execute() function could be changed to PDO_PARAM_AUTO for less BC breaks.+For compatibility the execute() function could be changed to PDO_PARAM_ZVAL for less BC breaks on certain drivers.
internals/pdo/brainstorming.1260106236.txt.gz · Last modified: 2017/09/22 13:28 (external edit)

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