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132 lines
6.5 KiB
Markdown
132 lines
6.5 KiB
Markdown
# Select API Quickstart Guide [](https://slack.min.io)
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Traditional retrieval of objects is always as whole entities, i.e GetObject for a 5 GiB object, will always return 5 GiB of data. S3 Select API allows us to retrieve a subset of data by using simple SQL expressions. By using Select API to retrieve only the data needed by the application, drastic performance improvements can be achieved.
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You can use the Select API to query objects with following features:
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- Objects must be in CSV, JSON, or Parquet(*) format.
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- UTF-8 is the only encoding type the Select API supports.
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- GZIP or BZIP2 - CSV and JSON files can be compressed using GZIP, BZIP2, [ZSTD](https://facebook.github.io/zstd/), and streaming formats of [LZ4](https://lz4.github.io/lz4/), [S2](https://github.com/klauspost/compress/tree/master/s2#s2-compression) and [SNAPPY](http://google.github.io/snappy/).
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- Parquet API supports columnar compression for using GZIP, Snappy, LZ4. Whole object compression is not supported for Parquet objects.
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- Server-side encryption - The Select API supports querying objects that are protected with server-side encryption.
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Type inference and automatic conversion of values is performed based on the context when the value is un-typed (such as when reading CSV data). If present, the CAST function overrides automatic conversion.
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The [mc sql](https://min.io/docs/minio/linux/reference/minio-mc/mc-sql.html) command can be used for executing queries using the command line.
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(*) Parquet is disabled on the MinIO server by default. See below how to enable it.
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## Enabling Parquet Format
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Parquet is DISABLED by default since hostile crafted input can easily crash the server.
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If you are in a controlled environment where it is safe to assume no hostile content can be uploaded to your cluster you can safely enable Parquet.
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To enable Parquet set the environment variable `MINIO_API_SELECT_PARQUET=on`.
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## Example using Python API
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### 1. Prerequisites
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- Install MinIO Server from [here](https://min.io/docs/minio/linux/index.html#procedure).
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- Familiarity with AWS S3 API.
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- Familiarity with Python and installing dependencies.
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### 2. Install boto3
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Install `aws-sdk-python` from AWS SDK for Python official docs [here](https://aws.amazon.com/sdk-for-python/)
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### 3. Example
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As an example, let us take a gzip compressed CSV file. Without S3 Select, we would need to download, decompress and process the entire CSV to get the data you needed. With Select API, can use a simple SQL expression to return only the data from the CSV you’re interested in, instead of retrieving the entire object. Following Python example shows how to retrieve the first column `Location` from an object containing data in CSV format.
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Please replace ``endpoint_url``,``aws_access_key_id``, ``aws_secret_access_key``, ``Bucket`` and ``Key`` with your local setup in this ``select.py`` file.
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```py
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#!/usr/bin/env/env python3
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import boto3
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s3 = boto3.client('s3',
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endpoint_url='http://localhost:9000',
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aws_access_key_id='minio',
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aws_secret_access_key='minio123',
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region_name='us-east-1')
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r = s3.select_object_content(
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Bucket='mycsvbucket',
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Key='sampledata/TotalPopulation.csv.gz',
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ExpressionType='SQL',
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Expression="select * from s3object s where s.Location like '%United States%'",
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InputSerialization={
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'CSV': {
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"FileHeaderInfo": "USE",
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},
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'CompressionType': 'GZIP',
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},
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OutputSerialization={'CSV': {}},
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)
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for event in r['Payload']:
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if 'Records' in event:
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records = event['Records']['Payload'].decode('utf-8')
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print(records)
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elif 'Stats' in event:
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statsDetails = event['Stats']['Details']
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print("Stats details bytesScanned: ")
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print(statsDetails['BytesScanned'])
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print("Stats details bytesProcessed: ")
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print(statsDetails['BytesProcessed'])
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```
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## 4. Run the Program
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Upload a sample dataset to MinIO using the following commands.
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```sh
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curl "https://population.un.org/wpp/Download/Files/1_Indicators%20(Standard)/CSV_FILES/WPP2019_TotalPopulationBySex.csv" > TotalPopulation.csv
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mc mb myminio/mycsvbucket
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gzip TotalPopulation.csv
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mc cp TotalPopulation.csv.gz myminio/mycsvbucket/sampledata/
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```
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Now let us proceed to run our select example to query for `Location` which matches `United States`.
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```sh
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$ python3 select.py
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840,United States of America,2,Medium,1950,1950.5,79233.218,79571.179,158804.395
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840,United States of America,2,Medium,1951,1951.5,80178.933,80726.116,160905.035
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840,United States of America,2,Medium,1952,1952.5,81305.206,82019.632,163324.851
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840,United States of America,2,Medium,1953,1953.5,82565.875,83422.307,165988.190
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....
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....
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....
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Stats details bytesScanned:
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6758866
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Stats details bytesProcessed:
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25786743
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```
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For a more detailed SELECT SQL reference, please see [here](https://docs.aws.amazon.com/AmazonS3/latest/dev/s3-glacier-select-sql-reference-select.html)
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## 5. Explore Further
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- [Use `mc` with MinIO Server](https://min.io/docs/minio/linux/reference/minio-mc.html)
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- [Use `mc sql` with MinIO Server](https://min.io/docs/minio/linux/reference/minio-mc/mc-sql.html#command-mc.sql)
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- [Use `minio-go` SDK with MinIO Server](https://min.io/docs/minio/linux/developers/go/minio-go.html)
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- [Use `aws-cli` with MinIO Server](https://min.io/docs/minio/linux/integrations/aws-cli-with-minio.html)
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- [The MinIO documentation website](https://min.io/docs/minio/linux/index.html)
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## 6. Implementation Status
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- Full AWS S3 [SELECT SQL](https://docs.aws.amazon.com/AmazonS3/latest/dev/s3-glacier-select-sql-reference-select.html) syntax is supported.
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- All [operators](https://docs.aws.amazon.com/AmazonS3/latest/dev/s3-glacier-select-sql-reference-operators.html) are supported.
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- All aggregation, conditional, type-conversion and string functions are supported.
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- JSON path expressions such as `FROM S3Object[*].path` are not yet evaluated.
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- Large numbers (outside of the signed 64-bit range) are not yet supported.
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- The Date [functions](https://docs.aws.amazon.com/AmazonS3/latest/dev/s3-glacier-select-sql-reference-date.html) `DATE_ADD`, `DATE_DIFF`, `EXTRACT` and `UTCNOW` along with type conversion using `CAST` to the `TIMESTAMP` data type are currently supported.
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- AWS S3's [reserved keywords](https://docs.aws.amazon.com/AmazonS3/latest/dev/s3-glacier-select-sql-reference-keyword-list.html) list is not yet respected.
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- CSV input fields (even quoted) cannot contain newlines even if `RecordDelimiter` is something else.
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