Adminer Parquet driver (read-only)

A database driver/plugin that adds Apache Parquet support to Adminer 5.x, built against Adminer's extension/driver API.

Parquet is a columnar on-disk file format, not a database server. This driver lets you browse and read Parquet files through the normal Adminer UI: list files as tables, inspect their schema, and run SELECT with search, sort, and paging. It is read-only — Parquet files are treated as immutable analytical data.

It is backed by the pure-PHP reader flow-php/parquet, so there is no native library, FFI, or PDO driver to install — just PHP with ext-bcmath and ext-zlib.

Adminer's driver API expects three classes in the Adminer namespace plus a set of free functions (see docs/reference-driver.inc.php and docs/reference-sqlite.inc.php, kept locally for reference):

Because there is no SQL engine behind Parquet, Driver::select() does not build a SQL string. It reads rows directly from the file via flow-php/parquet (Reader::php()->read($file)->values($columns, $limit, $offset)) and applies Adminer's WHERE / ORDER BY / LIMIT / paging in PHP. Total row counts come straight from the Parquet footer metadata (->metadata()->rowsNumber()), so they are cheap even for large files.

A Parquet file is a single flat table. Adminer's world is server → database → schema → table, mapped as:

.parq and .pqt are accepted as alternate extensions.

• PHP 8.3+ with ext-bcmath and ext-zlib

• The zstd PHP extension (PECL) — many Parquet files are Zstandard-compressed, and flow-php/parquet needs ext-zstd to read those column chunks. Building it requires the PHP development toolchain (phpize) and PECL:

  # Debian/Ubuntu — install the build toolchain first:
  sudo apt-get install php-dev php-pear      # provides phpize + pecl
  
  # then build & install the extension:
  sudo pecl install zstd

  Then enable it. The simplest way is to add the line directly to your php.ini (run php --ini to find the file(s) in use — note the CLI and web-server SAPIs often use different ini files, so add it to both):

  ; php.ini
  extension=zstd.so

  On Debian/Ubuntu you can instead use the per-extension ini + phpenmod, which enables it for every SAPI at once:

  echo "extension=zstd.so" | sudo tee /etc/php/$(php -r 'echo PHP_MAJOR_VERSION.".".PHP_MINOR_VERSION;')/mods-available/zstd.ini
  sudo phpenmod zstd

  Restart your PHP/web server afterwards, then verify with php -m | grep zstd (and check the web SAPI too, e.g. via a phpinfo() page). Snappy- and gzip-compressed Parquet work without it, but zstd is the common default from Spark/Arrow/DuckDB exports.

• composer require flow-php/parquet

• Adminer 5.x

This is a drop-in driver. Adminer globs adminer-plugins/*.php at startup and includes each file, so you only need to place the files there — the top-level add_driver("parquet", "Parquet") call registers the driver and Parquet appears in the System dropdown. No adminer_object() bootstrap required.

Lay it out next to your adminer.php:

your-adminer-dir/
├── adminer.php
├── adminer-plugins/          # folder name must be exactly this
│   ├── parquet-driver.php     # the driver
│   └── parquet-login.php      # login-form relabeling (optional but recommended)
└── vendor/                   # from: composer require flow-php/parquet

Steps:

# in your-adminer-dir/
composer require flow-php/parquet
mkdir -p adminer-plugins
cp /path/to/parquet-driver.php /path/to/parquet-login.php adminer-plugins/

The single-file adminer.php has no Composer autoloader of its own, so parquet-driver.php pulls in vendor/autoload.php itself — it looks both next to the plugin (adminer-plugins/vendor/) and next to adminer.php (../vendor/), so either location for composer require works.

Verify the reader independently of Adminer:

php -r 'require "vendor/autoload.php";
  $f = \Flow\Parquet\Reader::php()->read("data.parquet");
  echo $f->metadata()->rowsNumber()." rows\n";
  foreach ($f->values([], 5) as $r) echo json_encode($r)."\n";'

On Adminer's login screen:

• System: Parquet
• Parquet path: a directory of .parquet files (e.g. /var/data/warehouse/) or a single file (e.g. /var/data/events.parquet)
• Username / Password: ignored

Files under the directory are listed recursively as tables; open one to browse it, search/sort columns, and page through rows.

This driver is read-only by design — Parquet is an immutable columnar file format read here through the pure-PHP flow-php/parquet library, which has no write path in this integration. Unlike the DuckDB driver (whose read-only open is an optional, reversible safety setting), there is no toggle to make Parquet writable: every mutating hook in parquet-driver.php (insert/update/delete, create/alter/drop, indexes, foreign keys, triggers, transactions) returns false, and support() advertises only columns, table, and dump.

Consequence: browsing and SELECT (search, sort, paging, export) work; anything that would change data is unavailable.

Adminer still renders its per-row edit links (and the insert/edit forms) for Parquet tables, but because the driver exposes no writable backend those pages end in an error when opened or submitted. This is expected, not a bug: Parquet has no primary key or rowid to address a single row by, and there is nothing to save changes to. Use select (the table browse view) to inspect data; ignore the edit links.

If you need to modify the data, do it at the source that produces the Parquet files (Spark, Arrow, DuckDB, pandas, …) and re-export; Adminer is a viewer here.

Browsing the file/table list (recursive), viewing a table's columns and types, row counts and file sizes, SELECT with search (=, <, >, <=, >=, !=, LIKE, IN, IS NULL, …), multi-column sort, paging, a reference CREATE TABLE reconstruction, and export (dump).

Nested LIST / MAP / STRUCT columns are shown JSON-encoded (marked "nested" in the field list).

Note: this driver is read-only — there is no writable mode for Parquet. See Read-only mode, including why the Edit links lead to an error.

Everything that mutates or requires a SQL engine — the free-text SQL command page, INSERT/UPDATE/DELETE, CREATE/ALTER/DROP, indexes, foreign keys, triggers, stored routines, transactions, and EXPLAIN. Parquet is read-only here by design; joins and aggregations across files are not available (no SQL engine).

parquet-driver.php       the driver (self-contained, namespace Adminer) — goes in adminer-plugins/
parquet-login.php        login-form relabeling helper — goes in adminer-plugins/
composer.json            dependencies (flow-php/parquet, ext-bcmath, ext-zlib)
docs/                    local copies of the Adminer API files used as reference