silverstripe-framework/docs/en/04_Changelogs/4.3.0.md
Sam Minnée 5b7a84141b NEW: Add Hierarchy::prepopulate_numchildren_cache() (#8380)
* NEW: Add Hierarchy::prepopulate_numchildren_cache()
API: Hierarchy::stageChildren() customisations must be applied to the base class and not include record-specific behaviour.

Adds the ability to prepopulate the cache for Hierarchy::numChildren()
in a batch.

Note that this optimisation means that stageChildren() is not called on
each record in order to calculate numChildren(). This means that the
structure of the stageChildren() query must be the same for all records
and the behaviour cannot be customised only for a subclass of the base
data class. For example, apply your customisations to SiteTree and not
a subclass.

This is an useful part of optimising the query count on tree generation.
See https://github.com/silverstripe/silverstripe-framework/issues/8379

* NEW: Add Hierarchy::prepopulateTreeDataCache()

This provides a more extensible way of preopulating caches for optimised
tree generation.

Fixes https://github.com/silverstripe/silverstripe-framework/issues/8391
2018-09-25 12:25:23 +12:00

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# 4.3.0
## Overview {#overview}
- `DataList::column()` now returns all values and not just "distinct" values from a column as per the API docs
- `DataList`, `ArrayList` and `UnsavedRalationList` all have `columnUnique()` method for fetching distinct column values
- Take care with `stageChildren()` overrides. `Hierarchy::numChildren() ` results will only make use of `stageChildren()` customisations that are applied to the base class and don't include record-specific behaviour.
## Upgrading {#upgrading}
### Fetching distinct column values on DataList
Prior to this release `DataList` would erroneously return a distinct list of values from a column on an object.
If this behaviour is still required, please use `columnUnique()` instead.