[PHP] Extract DatabaseRowsReader from MySQLDumpProducer

[adamziel]

Extracts DatabaseRowsReader from MySQLDumpProducer so database records can be consumed without generating SQL first.

MySQLDumpProducer now owns a reader and remains responsible for SQL formatting, oversized values, and the dump lifecycle. The reader owns table discovery, metadata, bounded primary-key queries, exclusions, and cursor state.

This does not change dump output. The child PR #578 uses the reader to process structured live database records directly.

Example

$reader = new DatabaseRowsReader($pdo, [
    "batch_size" => 250,
]);
$reader->initialize_tables_to_process();

while ($reader->move_to_next_table()) {
    while ($reader->next_record()) {
        $table = $reader->get_current_table();
        $record = $reader->get_current_record();

        process_record($table, $record);
        $reader->clear_current_record();
    }
}

Testing

The existing dump producer tests cover batch boundaries, composite keys, exclusions, data types, and cursor resume. PHP 7.2 compatibility, PHPStan, and CI pass.

[github-actions]

Pull pipeline performance — large-directory

Site: large-directory · 2,000+ plus targeted file-transfer scenarios files · 10,000 posts · 25,000 postmeta · PHP 8.5.9

Stage	PR	trunk	Δ	Status	Details
playground-sqlite-db-pull	9.59 s	9.60 s	⚪ -1 ms (-0.0%)	✓	condition=db-pull in PHP.wasm runtime=php.wasm 8.3 wp_mysql_parser=enabled mode=lexer native_lexer=verified native_token_stream=WP_MySQL_Native_Token_Stream native_token_count=18 native_parser=selected trunk: condition=db-pull in PHP.wasm runtime=php.wasm 8.3 wp_mysql_parser=enabled mode=lexer native_lexer=verified native_token_stream=WP_MySQL_Native_Token_Stream native_token_count=18 native_parser=selected
playground-sqlite-db-apply	3.69 s	3.69 s	⚪ +2 ms (+0.1%)	✓	condition=db-apply to SQLite in PHP.wasm runtime=php.wasm 8.3 wp_mysql_parser=enabled mode=parser native_lexer=verified native_token_stream=WP_MySQL_Native_Token_Stream native_token_count=18 native_parser=verified native_ast=WP_MySQL_Native_Parser_Node sqlite_driver_parser=verified trunk: condition=db-apply to SQLite in PHP.wasm runtime=php.wasm 8.3 wp_mysql_parser=enabled mode=parser native_lexer=verified native_token_stream=WP_MySQL_Native_Token_Stream native_token_count=18 native_parser=verified native_ast=WP_MySQL_Native_Parser_Node sqlite_driver_parser=verified
Total	13.28 s	13.28 s	⚪ +1 ms (+0.0%)

_{Numbers carry runner noise; treat single-run deltas as directional, not authoritative.}

_{📈 Trunk performance history — commit-by-commit timeline.}