Move identity cache from PHP into the Rust extension

The PHP-side cache from #391 fixed the correctness regression but added
27-31% to translator-style re-entry workloads — every accessor probes a
PHP zend_array that, at full-walk scale, holds 4.8M entries, and PHP
still allocates a fresh wrapper before the cache check gets a chance
to drop it.

This moves the cache to where it can actually skip work. WP_MySQL_Native_Ast
now carries a RefCell<HashMap<usize, ZBox<ZendObject>>>; cached_node_zval
returns a Zval pointing at the stored wrapper with refcount bumped on a
hit, so the allocation and four zend_update_property calls of the
construction path are gone. Every accessor (get_first_child_node,
get_descendants, etc.) routes through this helper.

PHP-side cache disappears: WP_MySQL_Native_Parser_Node goes back to
plain bridge calls, the WP_MySQL_Native_AST_Cache holder is removed.
Mutation semantics are unchanged — materialize_native_children still
flips was_mutated and copies the same wrappers (now interned by Rust)
into $this->children, so any caller mutation made before append_child
still survives.

Tokens are not yet interned. The public token API has no mutators and
no caller in this repo relies on token identity; if that changes we
extend node_cache with a token map.

Author: adamziel

packages/mysql-on-sqlite/src/load.php

@@ -27,7 +27,6 @@
 
 if ( class_exists( 'WP_MySQL_Native_Parser', false ) ) {
 	require_once __DIR__ . '/mysql/native/mysql-rust-bridge.php';
-	require_once __DIR__ . '/mysql/native/class-wp-mysql-native-ast-cache.php';
 	require_once __DIR__ . '/mysql/native/class-wp-mysql-native-parser-node.php';
 	require_once __DIR__ . '/mysql/native/class-wp-mysql-parser.php';
 } else {

packages/mysql-on-sqlite/src/mysql/native/class-wp-mysql-native-ast-cache.php

@@ -8,49 +8,19 @@
  * caller actually walks the tree. On the first mutation (append_child or
  * merge_fragment), the node materializes its children into the inherited
  * `$children` array and behaves like a plain WP_Parser_Node from then on.
- *
- * Wrappers returned by accessors are interned through a per-AST identity
- * map (WP_MySQL_Native_AST_Cache) so two reads of the same logical node
- * yield the same PHP instance. This preserves the WP_Parser_Node contract
- * that mutations performed on a child via `get_first_child_node()` remain
- * visible when the same child is reached again, including after the parent
- * has materialized.
  */
 class WP_MySQL_Native_Parser_Node extends WP_Parser_Node {
 	private $native_ast        = null;
 	private $native_node_index = null;
 	private $was_mutated       = false;
 
-	/**
-	 * Per-AST identity map shared between every interned wrapper.
-	 *
-	 * Created lazily on the first child access; the root wrapper is the
-	 * first entry. Children inherit the same cache instance by reference.
-	 *
-	 * @var WP_MySQL_Native_AST_Cache|null
-	 */
-	private $cache = null;
-
 	public function __construct( $rule_id, $rule_name, $native_ast = null, $native_node_index = null ) {
 		parent::__construct( $rule_id, $rule_name );
 
 		$this->native_ast        = $native_ast;
 		$this->native_node_index = $native_node_index;
 	}
 
-	/**
-	 * Native node index in the Rust-owned arena.
-	 *
-	 * Exposed so the identity cache can key on it. Returns null after
-	 * the wrapper has materialized — at that point the node is detached
-	 * from the native arena and behaves like a plain WP_Parser_Node.
-	 *
-	 * @return int|null
-	 */
-	public function get_native_node_index(): ?int {
-		return $this->native_node_index;
-	}
-
 	/** @inheritDoc */
 	public function append_child( $node ) {
 		$this->materialize_native_children();
@@ -95,15 +65,15 @@ public function get_first_child() {
 		if ( $this->was_mutated() ) {
 			return parent::get_first_child();
 		}
-		return $this->intern( wp_sqlite_mysql_native_ast_get_first_child( $this->native_ast, $this->native_node_index ) );
+		return wp_sqlite_mysql_native_ast_get_first_child( $this->native_ast, $this->native_node_index );
 	}
 
 	/** @inheritDoc */
 	public function get_first_child_node( ?string $rule_name = null ): ?WP_Parser_Node {
 		if ( $this->was_mutated() ) {
 			return parent::get_first_child_node( $rule_name );
 		}
-		return $this->intern( wp_sqlite_mysql_native_ast_get_first_child_node( $this->native_ast, $this->native_node_index, $rule_name ) );
+		return wp_sqlite_mysql_native_ast_get_first_child_node( $this->native_ast, $this->native_node_index, $rule_name );
 	}
 
 	/** @inheritDoc */
@@ -119,7 +89,7 @@ public function get_first_descendant_node( ?string $rule_name = null ): ?WP_Pars
 		if ( $this->was_mutated() ) {
 			return parent::get_first_descendant_node( $rule_name );
 		}
-		return $this->intern( wp_sqlite_mysql_native_ast_get_first_descendant_node( $this->native_ast, $this->native_node_index, $rule_name ) );
+		return wp_sqlite_mysql_native_ast_get_first_descendant_node( $this->native_ast, $this->native_node_index, $rule_name );
 	}
 
 	/** @inheritDoc */
@@ -135,15 +105,15 @@ public function get_children(): array {
 		if ( $this->was_mutated() ) {
 			return parent::get_children();
 		}
-		return $this->intern_all( wp_sqlite_mysql_native_ast_get_children( $this->native_ast, $this->native_node_index ) );
+		return wp_sqlite_mysql_native_ast_get_children( $this->native_ast, $this->native_node_index );
 	}
 
 	/** @inheritDoc */
 	public function get_child_nodes( ?string $rule_name = null ): array {
 		if ( $this->was_mutated() ) {
 			return parent::get_child_nodes( $rule_name );
 		}
-		return $this->intern_nodes( wp_sqlite_mysql_native_ast_get_child_nodes( $this->native_ast, $this->native_node_index, $rule_name ) );
+		return wp_sqlite_mysql_native_ast_get_child_nodes( $this->native_ast, $this->native_node_index, $rule_name );
 	}
 
 	/** @inheritDoc */
@@ -159,15 +129,15 @@ public function get_descendants(): array {
 		if ( $this->was_mutated() ) {
 			return parent::get_descendants();
 		}
-		return $this->intern_all( wp_sqlite_mysql_native_ast_get_descendants( $this->native_ast, $this->native_node_index ) );
+		return wp_sqlite_mysql_native_ast_get_descendants( $this->native_ast, $this->native_node_index );
 	}
 
 	/** @inheritDoc */
 	public function get_descendant_nodes( ?string $rule_name = null ): array {
 		if ( $this->was_mutated() ) {
 			return parent::get_descendant_nodes( $rule_name );
 		}
-		return $this->intern_nodes( wp_sqlite_mysql_native_ast_get_descendant_nodes( $this->native_ast, $this->native_node_index, $rule_name ) );
+		return wp_sqlite_mysql_native_ast_get_descendant_nodes( $this->native_ast, $this->native_node_index, $rule_name );
 	}
 
 	/** @inheritDoc */
@@ -198,128 +168,12 @@ private function was_mutated(): bool {
 		return $this->was_mutated;
 	}
 
-	/**
-	 * Intern a single accessor return value through the per-AST cache.
-	 *
-	 * Tokens and nulls pass through untouched. Native node wrappers are
-	 * keyed on their `native_node_index`: on cache miss, the freshly
-	 * constructed wrapper is stored and given the cache reference; on
-	 * cache hit, the canonical instance is returned and the new wrapper
-	 * is discarded so callers see stable identity and surviving mutations.
-	 *
-	 * @param mixed $value Return value from the Rust bridge.
-	 * @return mixed
-	 */
-	private function intern( $value ) {
-		if ( ! $value instanceof WP_MySQL_Native_Parser_Node ) {
-			return $value;
-		}
-
-		$cache = $this->ensure_cache();
-		$index = $value->native_node_index;
-		if ( null === $index ) {
-			return $value;
-		}
-		if ( isset( $cache->nodes[ $index ] ) ) {
-			return $cache->nodes[ $index ];
-		}
-		$value->cache           = $cache;
-		$cache->nodes[ $index ] = $value;
-		return $value;
-	}
-
-	/**
-	 * Intern every entry in an accessor return array.
-	 *
-	 * Hot path: this runs once per descendant when a caller walks the tree,
-	 * so cache lookup and the cache-miss write are inlined and the cache
-	 * reference is hoisted out of the loop.
-	 *
-	 * @param array $values
-	 * @return array
-	 */
-	private function intern_all( array $values ): array {
-		if ( ! $values ) {
-			return $values;
-		}
-		$cache = $this->cache ?? $this->ensure_cache();
-		$nodes = &$cache->nodes;
-		foreach ( $values as $i => $value ) {
-			if ( ! $value instanceof WP_MySQL_Native_Parser_Node ) {
-				continue;
-			}
-			$index = $value->native_node_index;
-			if ( null === $index ) {
-				continue;
-			}
-			if ( isset( $nodes[ $index ] ) ) {
-				$values[ $i ] = $nodes[ $index ];
-			} else {
-				$value->cache    = $cache;
-				$nodes[ $index ] = $value;
-			}
-		}
-		return $values;
-	}
-
-	/**
-	 * Intern array of guaranteed-node results (no token/null mixing).
-	 *
-	 * Used by `get_child_nodes()` / `get_descendant_nodes()` whose Rust
-	 * bridge returns only WP_MySQL_Native_Parser_Node instances. Skips
-	 * the per-item `instanceof` check that intern_all() must do for the
-	 * mixed `get_children()` / `get_descendants()` arrays.
-	 *
-	 * @param array $values
-	 * @return array
-	 */
-	private function intern_nodes( array $values ): array {
-		if ( ! $values ) {
-			return $values;
-		}
-		$cache = $this->cache ?? $this->ensure_cache();
-		$nodes = &$cache->nodes;
-		foreach ( $values as $i => $value ) {
-			$index = $value->native_node_index;
-			if ( isset( $nodes[ $index ] ) ) {
-				$values[ $i ] = $nodes[ $index ];
-			} else {
-				$value->cache    = $cache;
-				$nodes[ $index ] = $value;
-			}
-		}
-		return $values;
-	}
-
-	/**
-	 * Lazily build (or reuse) the per-AST identity map.
-	 *
-	 * The root wrapper is constructed without a cache, so the first time
-	 * any accessor needs to intern a child, it creates the cache and
-	 * registers itself as the root entry. Subsequent interns on this
-	 * wrapper or any descendant share the same cache by reference.
-	 *
-	 * @return WP_MySQL_Native_AST_Cache
-	 */
-	private function ensure_cache(): WP_MySQL_Native_AST_Cache {
-		if ( null === $this->cache ) {
-			$this->cache = new WP_MySQL_Native_AST_Cache();
-			if ( null !== $this->native_node_index ) {
-				$this->cache->nodes[ $this->native_node_index ] = $this;
-			}
-		}
-		return $this->cache;
-	}
-
 	private function materialize_native_children(): void {
 		if ( $this->was_mutated ) {
 			return;
 		}
 
-		// Pull children through the cache so any wrapper a caller already
-		// mutated via get_first_child_node() etc. survives the transition
-		// into $this->children — same instance, same mutations.
-		$this->children          = $this->intern_all( wp_sqlite_mysql_native_ast_get_children( $this->native_ast, $this->native_node_index ) );
+		$this->children          = wp_sqlite_mysql_native_ast_get_children( $this->native_ast, $this->native_node_index );
 		$this->native_ast        = null;
 		$this->native_node_index = null;
 		$this->was_mutated       = true;