Parquet S3 Foreign Data Wrapper for PostgreSQL

This PostgreSQL extension is a Foreign Data Wrapper (FDW) for accessing Parquet file on local file system and Amazon S3. This version of parquet_s3_fdw can work for PostgreSQL 13.

Parquet foreign data wrapper supporting S3 access for PostgreSQL.

This code is based on parquet_fdwcreated by adjust GmbH.

Installation

1. Install dependent libraries

parquet_s3_fdw requires libarrow and libparquet installed in your system (requires version 0.15, for previous versions use branch arrow-0.14). Please refer to building guide.

AWS SDK for C++ (libaws-cpp-sdk-core libaws-cpp-sdk-s3) is also required (Confirmed version is 1.8.14).

Attention!
We reccomend to build libarrow, libparquet and AWS SDK for C++ from the source code. We failed to link if using pre-compiled binaries because gcc version is different between arrow and AWS SDK.

2. Build and install parquet_s3_fdw

make install

or in case when PostgreSQL is installed in a custom location:

make install PG_CONFIG=/path/to/pg_config

It is possible to pass additional compilation flags through either custom CCFLAGS or standard PG_CFLAGS, PG_CXXFLAGS, PG_CPPFLAGS variables.

Usage

Load extension

CREATE EXTENSION parquet_s3_fdw;

Create server

CREATE SERVER parquet_s3_srv FOREIGN DATA WRAPPER parquet_s3_fdw;

If using MinIO instead of AWS S3, please use use_minio option for create server.

CREATE SERVER parquet_s3_srv FOREIGN DATA WRAPPER parquet_s3_fdw OPTIONS (use_minio 'true');

Create user mapping

You have to specify user name and password if accessing Amazon S3.

CREATE USER MAPPING FOR public SERVER parquet_s3_srv OPTIONS (user 's3user', password 's3password');

Create foreign table

Now you should be able to create foreign table from Parquet files. Currently parquet_s3_fdw supports the following column types (to be extended shortly):

Parquet type	SQL type
INT32	INT4
INT64	INT8
FLOAT	FLOAT4
DOUBLE	FLOAT8
TIMESTAMP	TIMESTAMP
DATE32	DATE
STRING	TEXT
BINARY	BYTEA
LIST	ARRAY

Currently parquet_s3_fdw doesn't support structs and nested lists.

Following options are supported:

filename - space separated list of paths to Parquet files to read. You can specify the path on AWS S3 by starting with s3://. The mix of local path and S3 path is not supported;
dirname - path to directory having Parquet files to read;
sorted - space separated list of columns that Parquet files are presorted by; that would help postgres to avoid redundant sorting when running query with ORDER BY clause or in other cases when having a presorted set is beneficial (Group Aggregate, Merge Join);
use_mmap - whether memory map operations will be used instead of file read operations (default false);
use_threads - enables arrow's parallel columns decoding/decompression (default false).

GUC variables:

parquet_fdw.use_threads - global switch that allow user to enable or disable threads (default true).

Example:

CREATE FOREIGN TABLE userdata (
    id           int,
    first_name   text,
    last_name    text
)
SERVER parquet_s3_srv
OPTIONS (
    filename 's3://bucket/dir/userdata1.parquet'
);

Access foreign table

SELECT * FROM userdata;

Parallel queries

parquet_s3_fdw also supports parallel query execution (not to confuse with multi-threaded decoding feature of arrow). It is disabled by default; to enable it run ANALYZE command on the table. The reason behind this is that without statistics postgres may end up choosing a terrible parallel plan for certain queries which would be much worse than a serial one (e.g. grouping by a column with large number of distinct values).

Import

parquet_s3_fdw also supports IMPORT FOREIGN SCHEMA command to discover parquet files in the specified directory on filesystem and create foreign tables according to those files. It can be used as follows:

IMPORT FOREIGN SCHEMA "/path/to/directory"
FROM SERVER parquet_s3_srv
INTO public;

It is important that remote_schema here is a path to a local filesystem directory and is double quoted.

Another way to import parquet files into foreign tables is to use import_parquet_s3 or import_parquet_s3_explicit:

CREATE FUNCTION import_parquet_s3(
    tablename   text,
    schemaname  text,
    servername  text,
    userfunc    regproc,
    args        jsonb,
    options     jsonb)

CREATE FUNCTION import_parquet_s3_explicit(
    tablename   text,
    schemaname  text,
    servername  text,
    attnames    text[],
    atttypes    regtype[],
    userfunc    regproc,
    args        jsonb,
    options     jsonb)

The only difference between import_parquet_s3 and import_parquet_s3_explicit is that the latter allows to specify a set of attributes (columns) to import. attnames and atttypes here are the attributes names and attributes types arrays respectively (see the example below).

userfunc is a user-defined function. It must take a jsonb argument and return a text array of filesystem paths to parquet files to be imported. args is user-specified jsonb object that is passed to userfunc as its argument. A simple implementation of such function and its usage may look like this:

CREATE FUNCTION list_parquet_s3_files(args jsonb)
RETURNS text[] AS
$$
BEGIN
    RETURN array_agg(args->>'dir' || '/' || filename)
           FROM pg_ls_dir(args->>'dir') AS files(filename)
           WHERE filename ~~ '%.parquet';
END
$$
LANGUAGE plpgsql;

SELECT import_parquet_s3_explicit(
    'abc',
    'public',
    'parquet_srv',
    array['one', 'three', 'six'],
    array['int8', 'text', 'bool']::regtype[],
    'list_parquet_files',
    '{"dir": "/path/to/directory"}',
    '{"sorted": "one"}'
);

Features

Support SELECT of parquet file on local file system or Amazon S3.
Support MinIO access instead of Amazon S3.

Limitations

Modification (INSERT, UPDATE and DELETE) is not supported.
Transaction is not supported.
Cannot create a single foreign table using parquet files on both file system and Amazon S3.
AWS region is hard-coded as "ap-northeast-1". If you want to use another region, you need to modify the source code by changing "AP_NORTHEAST_1" in parquet_s3_fdw_connection.cpp.

Contributing

Opening issues and pull requests on GitHub are welcome.

License

Permission to use, copy, modify, and distribute this software and its documentation for any purpose, without fee, and without a written agreement is hereby granted, provided that the above copyright notice and this paragraph and the following two paragraphs appear in all copies.

See the LICENSE.md file for full details.

nathanqthai/parquet_s3_fdw