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rfc:extended-string-types-for-pdo [2017/03/09 16:09]
adambaratz add links describing cost of implicit casts
rfc:extended-string-types-for-pdo [2017/09/22 13:28]
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-====== PHP RFC: Extended String Types For PDO ====== 
-  * Version: 0.3 
-  * Date: 2017-02-16 
-  * Author: Adam Baratz adambaratz@php.net 
-  * Status: Voting 
-  * First Published at: https://wiki.php.net/rfc/extended-string-types-for-pdo 
-===== Introduction ===== 
-The "national character" type was introduced in [[http://www.contrib.andrew.cmu.edu/~shadow/sql/sql1992.txt|SQL-92]] (section 4.2.1). It's an open-ended type. The spec indicates that its meaning is defined by the implementation. [[https://dev.mysql.com/doc/refman/5.7/en/charset-national.html|MySQL]] and [[https://msdn.microsoft.com/en-GB/library/ms186939.aspx|Microsoft SQL Server]] use it to store Unicode data. 
-There is a different format for literals of this type. Instead of simply surrounding strings with quotes, an N is added as a prefix (e.g., N'string' instead of 'string'). When using emulated prepared statements -- the default behavior for pdo_mysql, the only one for pdo_dblib -- it's not possible to quote parameters using this format. This means that queries involving these columns will trigger implicit casts, which makes them more expensive. This issue affects [[https://www.sqlskills.com/blogs/jonathan/implicit-conversions-that-cause-index-scans/|MySQL]] and [[http://code.openark.org/blog/mysql/beware-of-implicit-casting|MSSQL]]. 
-There aren't many pdo_dblib users who comment regularly on the internals list, but the presence of a [[https://bugs.php.net/bug.php?id=60818|feature request]] and a [[https://github.com/php/php-src/pull/2017|pull request]] suggests that this is an impactful omission. 
-===== Proposal ===== 
-Three constants would be added to the pdo extension: 
-  - **PDO::PARAM_STR_NATL.** A new type, to be applied as a bitwise-OR to ''PDO::PARAM_STR''. It would indicate that the value should be quoted with the N-prefix. 
-  - **PDO::PARAM_STR_CHAR.** A new type, to be applied as a bitwise-OR to ''PDO::PARAM_STR''. It would indicate that the value should be quoted without the N-prefix. This would be used as an exception for when the ''PDO::ATTR_DEFAULT_STR_PARAM'' attribute is set to ''PDO::PARAM_STR_NATL''. 
-  - **PDO::ATTR_DEFAULT_STR_PARAM.** This driver attribute would indicate a value to bitwise-OR to ''PDO::PARAM_STR'' by default. 
-The parameter constants are more like ''PDO::PARAM_INPUT_OUTPUT'' than ''PDO::PARAM_STR''. They're flags to be applied to other parameters. This would also mean that code portability would be preserved. Drivers that don't need the hints for true prepared statements would ignore them. 
-  $db->quote('über', PDO::PARAM_STR | PDO::PARAM_STR_NATL); // N'über' 
-  $db->quote('A'); // 'A' 
-  $db->quote('über'); // N'über' 
-  $db->quote('A', PDO::PARAM_STR | PDO::PARAM_STR_CHAR); // 'A' 
-===== Backward Incompatible Changes ===== 
-This functionality would be strictly additive. Existing code would continue to work as it does. These constants wouldn't affect anything related to the character set used for connections. 
-====== Impact To Existing Extensions ====== 
-Drivers outside of php-src might have to be modified if they make assumptions about the structure of ''enum pdo_param_type''. They would have to be rebuilt since the ''PDO_DRIVER_API'' macro would be updated. 
-===== Proposed PHP Version(s) ===== 
-Next PHP 7.x. 
-===== Proposed Voting Choices ===== 
-Voting opened on 8 March 2017. It will close on the 17th at 0:00 UTC. This project requires a 50%+1 majority. 
-<doodle title="extended-string-types-for-pdo" auth="adambaratz" voteType="single" closed="false"> 
-   * Yes 
-   * No 
rfc/extended-string-types-for-pdo.txt · Last modified: 2017/09/22 13:28 (external edit)