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https://github.com/crunchydata/pg_parquet
Copy to/from Parquet in S3 from within PostgreSQL
https://github.com/crunchydata/pg_parquet
columnar data-ingestion data-migration parquet postgresql
Last synced: 7 days ago
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Copy to/from Parquet in S3 from within PostgreSQL
- Host: GitHub
- URL: https://github.com/crunchydata/pg_parquet
- Owner: CrunchyData
- License: other
- Created: 2024-09-04T21:11:44.000Z (4 months ago)
- Default Branch: main
- Last Pushed: 2024-12-06T00:50:39.000Z (16 days ago)
- Last Synced: 2024-12-13T21:09:21.377Z (9 days ago)
- Topics: columnar, data-ingestion, data-migration, parquet, postgresql
- Language: Rust
- Homepage:
- Size: 475 KB
- Stars: 376
- Watchers: 4
- Forks: 11
- Open Issues: 14
-
Metadata Files:
- Readme: README.md
- Contributing: CONTRIBUTING.md
- License: LICENSE
Awesome Lists containing this project
README
# pg_parquet
> Copy from/to Parquet files in PostgreSQL!
[](https://github.com/CrunchyData/pg_parquet/actions/workflows/ci.yml)
[](https://codecov.io/gh/CrunchyData/pg_parquet)
`pg_parquet` is a PostgreSQL extension that allows you to read and write [Parquet files](https://parquet.apache.org), which are located in `S3` or `file system`, from PostgreSQL via `COPY TO/FROM` commands. It depends on [Apache Arrow](https://arrow.apache.org/rust/arrow/) project to read and write Parquet files and [pgrx](https://github.com/pgcentralfoundation/pgrx) project to extend PostgreSQL's `COPY` command.
```sql
-- Copy a query result into Parquet in S3
COPY (SELECT * FROM table) TO 's3://mybucket/data.parquet' WITH (format 'parquet');
-- Load data from Parquet in S3
COPY table FROM 's3://mybucket/data.parquet' WITH (format 'parquet');
```
## Quick Reference
- [Installation From Source](#installation-from-source)
- [Usage](#usage)
- [Copy FROM/TO Parquet files TO/FROM Postgres tables](#copy-tofrom-parquet-files-fromto-postgres-tables)
- [Inspect Parquet schema](#inspect-parquet-schema)
- [Inspect Parquet metadata](#inspect-parquet-metadata)
- [Object Store Support](#object-store-support)
- [Copy Options](#copy-options)
- [Configuration](#configuration)
- [Supported Types](#supported-types)
- [Nested Types](#nested-types)
- [Postgres Support Matrix](#postgres-support-matrix)
## Installation From Source
After installing `Postgres`, you need to set up `rustup`, `cargo-pgrx` to build the extension.
```bash
# install rustup
> curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
# install cargo-pgrx
> cargo install cargo-pgrx
# configure pgrx
> cargo pgrx init --pg17 $(which pg_config)
# append the extension to shared_preload_libraries in ~/.pgrx/data-17/postgresql.conf
> echo "shared_preload_libraries = 'pg_parquet'" >> ~/.pgrx/data-17/postgresql.conf
# run cargo-pgrx to build and install the extension
> cargo pgrx run
# create the extension in the database
psql> "CREATE EXTENSION pg_parquet;"
```
## Usage
There are mainly 3 things that you can do with `pg_parquet`:
1. You can export Postgres tables/queries to Parquet files,
2. You can ingest data from Parquet files to Postgres tables,
3. You can inspect the schema and metadata of Parquet files.
### COPY to/from Parquet files from/to Postgres tables
You can use PostgreSQL's `COPY` command to read and write Parquet files. Below is an example of how to write a PostgreSQL table, with complex types, into a Parquet file and then to read the Parquet file content back into the same table.
```sql
-- create composite types
CREATE TYPE product_item AS (id INT, name TEXT, price float4);
CREATE TYPE product AS (id INT, name TEXT, items product_item[]);
-- create a table with complex types
CREATE TABLE product_example (
id int,
product product,
products product[],
created_at TIMESTAMP,
updated_at TIMESTAMPTZ
);
-- insert some rows into the table
insert into product_example values (
1,
ROW(1, 'product 1', ARRAY[ROW(1, 'item 1', 1.0), ROW(2, 'item 2', 2.0), NULL]::product_item[])::product,
ARRAY[ROW(1, NULL, NULL)::product, NULL],
now(),
'2022-05-01 12:00:00-04'
);
-- copy the table to a parquet file
COPY product_example TO '/tmp/product_example.parquet' (format 'parquet', compression 'gzip');
-- show table
SELECT * FROM product_example;
-- copy the parquet file to the table
COPY product_example FROM '/tmp/product_example.parquet';
-- show table
SELECT * FROM product_example;
```
### Inspect Parquet schema
You can call `SELECT * FROM parquet.schema()` to discover the schema of the Parquet file at given uri.
```sql
SELECT * FROM parquet.schema('/tmp/product_example.parquet') LIMIT 10;
uri | name | type_name | type_length | repetition_type | num_children | converted_type | scale | precision | field_id | logical_type
------------------------------+--------------+------------+-------------+-----------------+--------------+----------------+-------+-----------+----------+--------------
/tmp/product_example.parquet | arrow_schema | | | | 5 | | | | |
/tmp/product_example.parquet | id | INT32 | | OPTIONAL | | | | | 0 |
/tmp/product_example.parquet | product | | | OPTIONAL | 3 | | | | 1 |
/tmp/product_example.parquet | id | INT32 | | OPTIONAL | | | | | 2 |
/tmp/product_example.parquet | name | BYTE_ARRAY | | OPTIONAL | | UTF8 | | | 3 | STRING
/tmp/product_example.parquet | items | | | OPTIONAL | 1 | LIST | | | 4 | LIST
/tmp/product_example.parquet | list | | | REPEATED | 1 | | | | |
/tmp/product_example.parquet | element | | | OPTIONAL | 3 | | | | 5 |
/tmp/product_example.parquet | id | INT32 | | OPTIONAL | | | | | 6 |
/tmp/product_example.parquet | name | BYTE_ARRAY | | OPTIONAL | | UTF8 | | | 7 | STRING
(10 rows)
```
### Inspect Parquet metadata
You can call `SELECT * FROM parquet.metadata()` to discover the detailed metadata of the Parquet file, such as column statistics, at given uri.
```sql
SELECT uri, row_group_id, row_group_num_rows, row_group_num_columns, row_group_bytes, column_id, file_offset, num_values, path_in_schema, type_name FROM parquet.metadata('/tmp/product_example.parquet') LIMIT 1;
uri | row_group_id | row_group_num_rows | row_group_num_columns | row_group_bytes | column_id | file_offset | num_values | path_in_schema | type_name
------------------------------+--------------+--------------------+-----------------------+-----------------+-----------+-------------+------------+----------------+-----------
/tmp/product_example.parquet | 0 | 1 | 13 | 842 | 0 | 0 | 1 | id | INT32
(1 row)
```
```sql
SELECT stats_null_count, stats_distinct_count, stats_min, stats_max, compression, encodings, index_page_offset, dictionary_page_offset, data_page_offset, total_compressed_size, total_uncompressed_size FROM parquet.metadata('/tmp/product_example.parquet') LIMIT 1;
stats_null_count | stats_distinct_count | stats_min | stats_max | compression | encodings | index_page_offset | dictionary_page_offset | data_page_offset | total_compressed_size | total_uncompressed_size
------------------+----------------------+-----------+-----------+--------------------+--------------------------+-------------------+------------------------+------------------+-----------------------+-------------------------
0 | | 1 | 1 | GZIP(GzipLevel(6)) | PLAIN,RLE,RLE_DICTIONARY | | 4 | 42 | 101 | 61
(1 row)
```
You can call `SELECT * FROM parquet.file_metadata()` to discover file level metadata of the Parquet file, such as format version, at given uri.
```sql
SELECT * FROM parquet.file_metadata('/tmp/product_example.parquet')
uri | created_by | num_rows | num_row_groups | format_version
------------------------------+------------+----------+----------------+----------------
/tmp/product_example.parquet | pg_parquet | 1 | 1 | 1
(1 row)
```
You can call `SELECT * FROM parquet.kv_metadata()` to query custom key-value metadata of the Parquet file at given uri.
```sql
SELECT uri, encode(key, 'escape') as key, encode(value, 'escape') as value FROM parquet.kv_metadata('/tmp/product_example.parquet');
uri | key | value
------------------------------+--------------+---------------------
/tmp/product_example.parquet | ARROW:schema | /////5gIAAAQAAAA ...
(1 row)
```
## Object Store Support
`pg_parquet` supports reading and writing Parquet files from/to `S3` object store. Only the uris with `s3://` scheme is supported.
The simplest way to configure object storage is by creating the standard `~/.aws/credentials` and `~/.aws/config` files:
```bash
$ cat ~/.aws/credentials
[default]
aws_access_key_id = AKIAIOSFODNN7EXAMPLE
aws_secret_access_key = wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY
$ cat ~/.aws/config
[default]
region = eu-central-1
```
Alternatively, you can use the following environment variables when starting postgres to configure the S3 client:
- `AWS_ACCESS_KEY_ID`: the access key ID of the AWS account
- `AWS_SECRET_ACCESS_KEY`: the secret access key of the AWS account
- `AWS_REGION`: the default region of the AWS account
- `AWS_SHARED_CREDENTIALS_FILE`: an alternative location for the credentials file
- `AWS_CONFIG_FILE`: an alternative location for the config file
- `AWS_PROFILE`: the name of the profile from the credentials and config file (default profile name is `default`)
> [!NOTE]
> To be able to write into a object store location, you need to grant `parquet_object_store_write` role to your current postgres user.
> Similarly, to read from an object store location, you need to grant `parquet_object_store_read` role to your current postgres user.
## Copy Options
`pg_parquet` supports the following options in the `COPY TO` command:
- `format parquet`: you need to specify this option to read or write Parquet files which does not end with `.parquet[.]` extension,
- `row_group_size `: the number of rows in each row group while writing Parquet files. The default row group size is `122880`,
- `row_group_size_bytes `: the total byte size of rows in each row group while writing Parquet files. The default row group size bytes is `row_group_size * 1024`,
- `compression `: the compression format to use while writing Parquet files. The supported compression formats are `uncompressed`, `snappy`, `gzip`, `brotli`, `lz4`, `lz4raw` and `zstd`. The default compression format is `snappy`. If not specified, the compression format is determined by the file extension,
- `compression_level `: the compression level to use while writing Parquet files. The supported compression levels are only supported for `gzip`, `zstd` and `brotli` compression formats. The default compression level is `6` for `gzip (0-10)`, `1` for `zstd (1-22)` and `1` for `brotli (0-11)`.
`pg_parquet` supports the following options in the `COPY FROM` command:
- `format parquet`: you need to specify this option to read or write Parquet files which does not end with `.parquet[.]` extension,
- `match_by `: method to match Parquet file fields to PostgreSQL table columns. The available methods are `position` and `name`. The default method is `position`. You can set it to `name` to match the columns by their name rather than by their position in the schema (default). Match by `name` is useful when field order differs between the Parquet file and the table, but their names match.
## Configuration
There is currently only one GUC parameter to enable/disable the `pg_parquet`:
- `pg_parquet.enable_copy_hooks`: you can set this parameter to `on` or `off` to enable or disable the `pg_parquet` extension. The default value is `on`.
## Supported Types
`pg_parquet` has rich type support, including PostgreSQL's primitive, array, and composite types. Below is the table of the supported types in PostgreSQL and their corresponding Parquet types.
| PostgreSQL Type | Parquet Physical Type | Logical Type |
|-------------------|---------------------------|------------------|
| `bool` | BOOLEAN | |
| `smallint` | INT16 | |
| `integer` | INT32 | |
| `bigint` | INT64 | |
| `real` | FLOAT | |
| `oid` | INT32 | |
| `double` | DOUBLE | |
| `numeric`(1) | FIXED_LEN_BYTE_ARRAY(16) | DECIMAL(128) |
| `text` | BYTE_ARRAY | STRING |
| `json` | BYTE_ARRAY | STRING |
| `bytea` | BYTE_ARRAY | |
| `date` (2) | INT32 | DATE |
| `timestamp` | INT64 | TIMESTAMP_MICROS |
| `timestamptz` (3) | INT64 | TIMESTAMP_MICROS |
| `time` | INT64 | TIME_MICROS |
| `timetz`(3) | INT64 | TIME_MICROS |
| `geometry`(4) | BYTE_ARRAY | |
### Nested Types
| PostgreSQL Type | Parquet Physical Type | Logical Type |
|-------------------|---------------------------|------------------|
| `composite` | GROUP | STRUCT |
| `array` | element's physical type | LIST |
| `crunchy_map`(5) | GROUP | MAP |
> [!WARNING]
> - (1) `numeric` type is written the smallest possible memory width to parquet file as follows:
> * `numeric(P <= 9, S)` is represented as `INT32` with `DECIMAL` logical type
> * `numeric(9 < P <= 18, S)` is represented as `INT64` with `DECIMAL` logical type
> * `numeric(18 < P <= 38, S)` is represented as `FIXED_LEN_BYTE_ARRAY(9-16)` with `DECIMAL` logical type
> * `numeric(38 < P, S)` is represented as `BYTE_ARRAY` with `STRING` logical type
> * `numeric` is allowed by Postgres. (precision and scale not specified). These are represented by a default precision (38) and scale (16) instead of writing them as string. You get runtime error if your table tries to read or write a numeric value which is not allowed by the default precision and scale (22 integral digits before decimal point, 16 digits after decimal point).
> - (2) The `date` type is represented according to `Unix epoch` when writing to Parquet files. It is converted back according to `PostgreSQL epoch` when reading from Parquet files.
> - (3) The `timestamptz` and `timetz` types are adjusted to `UTC` when writing to Parquet files. They are converted back with `UTC` timezone when reading from Parquet files.
> - (4) The `geometry` type is represented as `BYTE_ARRAY` encoded as `WKB` when `postgis` extension is created. Otherwise, it is represented as `BYTE_ARRAY` with `STRING` logical type.
> - (5) `crunchy_map` is dependent on functionality provided by [Crunchy Bridge](https://www.crunchydata.com/products/crunchy-bridge). The `crunchy_map` type is represented as `GROUP` with `MAP` logical type when `crunchy_map` extension is created. Otherwise, it is represented as `BYTE_ARRAY` with `STRING` logical type.
> [!WARNING]
> Any type that does not have a corresponding Parquet type will be represented, as a fallback mechanism, as `BYTE_ARRAY` with `STRING` logical type. e.g. `enum`
## Postgres Support Matrix
`pg_parquet` supports the following PostgreSQL versions:
| PostgreSQL Major Version | Supported |
|--------------------------|-----------|
| 14 | ✅ |
| 15 | ✅ |
| 16 | ✅ |
| 17 | ✅ |