Available from version 1.32.0 (Gerrit change 456389)
Allows modifying the query used by Special:AncientPages.
Define function:
public static function onAncientPagesQuery( &$tables, &$conds, &$joinConds ) { ... }
Attach hook:

In extension.json:

	"Hooks": {
		"AncientPagesQuery": "MyExtensionHooks::onAncientPagesQuery"

For MediaWiki ≤1.25:

$wgHooks['AncientPagesQuery'][] = 'MyExtensionHooks::onAncientPagesQuery';
Called from:File(s): specials/SpecialAncientpages.php
Function(s): getQueryInfo

For more information about attaching hooks, see Manual:Hooks.
For examples of extensions using this hook, see Category:AncientPagesQuery extensions.