Fetching Databases notices in PDO
- Version: 1.0
- Date: 2009-13-10
- Author: Samuel ROZE email@example.com
- Status: Proposal for new patches
- Other formats:
The most important Databases have a functionality which returns some notices about the current query. These notices can be raised by the Database engine within a
DELETE query for instance or by a user function.
Generally, notices contain information about the parallel executions, about the number of fetched rows or about the performances of the query.
Get notices in PDO
In PDO, notices are stored into a “
notices” HashTable in the “
_pdo_dbh_t” structure. Notices are inserted into it by each Database's PDO's driver using:
zend_hash_next_index_insert(dbh->notices, &val, sizeof(zval *), NULL);
Where zval is the zval message string and val the allocated message string.
This is done if user have specified that he want to fetch notices using the setAttribute or the $option parameter on the PDO constructor.
- The name of the attribute is:
- The possible values are:
- PDO::NOTICES_NONE -- no fetching
- PDO::NOTICES_ARRAY -- fetching & noticeInfo returning value as an array
The name of the function that users have use to get notices is “
noticeInfo” which returns an
PDO::NOTICES_ARRAY is the value of
PDO::ATTR_LOG_NOTICES). The name is based on the “errorInfo” function to be more user-friendly.
noticeInfo is a
PDO function, not a
Get notices with PostgreSQL
Notices in PostgreSQL are raised in Pl/PgSQL with the “
RAISE NOTICE” command. They can be fetched using a notice processor defined by the “
PQsetNoticeProcessor” pointing on a “
_pdo_pgsql_notice” function which insert the message into
dbh->notices like the principle described into the Get notices in PDO part.
Get notices in MySQL
In MySQL, the working of notices is NOT like PostgreSQL. MySQL raise notices within simple queries like
DELETE. These notices cannot be raised by a user function.
In the MySQL C API, there's a function whose purpose is to get the number of warnings (and notices) for the last
query. This function is
mysql_warning_count result is greater than or equal to 1, there are warnings and we will get them. To get
these warning, we have to fetch results of the “SHOW WARNINGS” query.
mysql_warning_count() = 0, we can get the result of mysql_info which returns informations about the last
query. If the result of it is different to NULL, put the results into
Get notices in Oracle
In Oracle, notices can be raised by
DBMS_OUTPUT within a Pl/SQL function and some notifications are created by the Oracle Server.
OCI_EVENTS mode to specify that the application is interested in registering for and receiving notifications. This starts a dedicated listening thread for notifications on the client.”
Informations about notification callback which I didn't understand very much: http://download.oracle.com/docs/cd/B28359_01/appdev.111/b28395/oci09adv.htm#sthref1446
This is about getting notifications from Oracle: http://download.oracle.com/docs/cd/B28359_01/appdev.111/b28395/oci10new.htm#sthref1457
Global method for Oracle, in addition of these previous methods, to get DMBS_OUTPUT:
For others Databases
For others Databases who have a notice functionality, we have to reflect. Personally, i do not know which Databases...