MidCOM DBA level wrapper for the Midgard Query Builder.
This class must be used anyplace within MidCOM instead of the real midgard_query_builder object within the MidCOM Framework. This wrapper is required for the correct operation of many MidCOM services.
It essentially wraps the calls to midcom_helper__dbfactory::new_query_builder().
Normally you should never have to create an instance of this type directly, instead use the new_query_builder() method available in the MidCOM DBA API or the midcom_helper__dbfactory::new_query_builder() method which is still available.
If you have to do create the instance manually however, do not forget to call the \initialize() function after construction, or the creation callbacks will fail.
$hide_invisible : boolean
Set this element to true to hide all items which are currently invisible according to the approval/scheduling settings made using Metadata. This must be set before executing the query.
NOTE: Approval checks not implemented in collector yet
Be aware, that this setting will currently not use the QB to filter the objects accordingly, since there is no way yet to filter against parameters. This will mean some performance impact.
add_constraint(string $field, string $operator, mixed $value) : boolean
Add a constraint to the query.
| string | $field | The name of the MgdSchema property to query against. |
| string | $operator | The operator to use for the constraint, currently supported are <, <=, =, <>, >=, >, LIKE. LIKE uses the percent sign ('%') as a wildcard character. |
| mixed | $value | The value to compare against. It should be of the same type as the queried property. |
Indicating success.
add_constraint_with_property(string $field, string $operator, string $compare_field) : boolean
Add a constraint against another DB column to the query.
| string | $field | The name of the MgdSchema property to query against. |
| string | $operator | The operator to use for the constraint, currently supported are <, <=, =, <>, >=, >, LIKE. LIKE uses the percent sign ('%') as a wildcard character. |
| string | $compare_field | The field to compare against. |
Indicating success.
begin_group(string $operator = 'OR')
Creates a new logical group within the query. They are set in parentheses in the final SQL and will thus be evaluated with precedence over the normal out-of-group constraints.
While the call lets you decide whether all constraints within the group are AND'ed or OR'ed, only OR constraints make logically sense in this context, which is why this proxy function sets 'OR' as the default operator.
| string | $operator | One of 'OR' or 'AND' denoting the logical operation with which all constraints in the group are concatenated. |
add_order(string $field, string $direction = 'ASC') : boolean
Add an ordering constraint to the query builder.
| string | $field | The name of the MgdSchema property to query against. |
| string | $direction | One of 'ASC' or 'DESC' indicating ascending or descending ordering. The default is 'ASC'. |
Indicating success.
execute() : array<mixed,\midcom_core_dbaobject>
Execute the Querybuilder and call the appropriate callbacks from the associated class. This way, class authors have full control over what is actually returned to the application.
The calling sequence of all event handlers of the associated class is like this:
The result of the query builder.
count_unchecked() : integer
This is a mapping to the real count function of the Midgard Query Builder.
It is mainly intended when speed is important over accuracy, as it bypasses access control to get a fast impression of how many objects are available in a given query. It should always be kept in mind that this is a preliminary number, not a final one.
Use this function with care. The information you obtain in general is negligible, but a creative mind might nevertheless be able to take advantage of it.
The number of records matching the constraints without taking access control or visibility into account.
execute_unchecked()
Runs a query where limit and offset is taken into account <i>prior</i> to execution in the core.
This is useful in cases where you can safely assume read privileges on all objects, and where you would otherwise have to deal with huge resultsets.
Be aware that this might lead to empty resultsets "in the middle" of the actual full resultset when read privileges are missing.
get_result(integer $key, string $mode = null) : mixed
Get result by its index
| integer | $key | Requested index in result set |
| string | $mode | Execution mode: normal (default), unchecked, notwindowed |
False on failure (key does not exist), object given to constructor on success
_convert_class(string $classname) : string
Class resolution into the MidCOM DBA system.
Currently, Midgard requires the actual MgdSchema base classes to be used when dealing with the query, so we internally note the corresponding class information to be able to do correct typecasting later.
| string | $classname | The classname which should be converted. |
MgdSchema class name
_execute_and_check_privileges() : array<mixed,\midcom_core_dbaobject>
Executes the internal QB and filters objects based on ACLs and metadata
Array filtered by ACL and metadata visibility
execute_windowed() : array<mixed,\midcom_core_dbaobject>
Windowed querying.
Since ACLs/approval can hide objects on the PHP level, we cannot apply offsets directly to the QB, but must instead verify that all objects are visible to the current user before discarding them until the offset is met. To reduce memory consumption, a maximum number of entries is loaded in each iteration.
If we have a limit, we use it to dynamically adjust the window size between iterations to try to not load too much data, i.e. we start by querying the minimum number required to fill the offset and limit. If we end up with too few results, we do another iteration where we adjust the window according to how many we still need plus a padding that corresponds to the weighted number of denieds so far. This is repeated until the limit is filled or we run out of db results