Add select docs and fix return values for Select API (#6300)

master
Harshavardhana 6 years ago committed by kannappanr
parent 3de5a3157f
commit 5a4a57700b
  1. 11
      cmd/object-handlers.go
  2. 89
      docs/select/README.md
  3. 33
      docs/select/select.py
  4. 3
      pkg/s3select/helpers.go

@ -161,19 +161,22 @@ func (api objectAPIHandlers) SelectObjectContentHandler(w http.ResponseWriter, r
writeErrorResponse(w, ErrInvalidExpressionType, r.URL)
return
}
if len(selectReq.Expression) >= (256 * 1000) {
if len(selectReq.Expression) >= s3select.MaxExpressionLength {
writeErrorResponse(w, ErrExpressionTooLong, r.URL)
return
}
if selectReq.InputSerialization.CSV.FileHeaderInfo != CSVFileHeaderInfoUse &&
selectReq.InputSerialization.CSV.FileHeaderInfo != CSVFileHeaderInfoNone &&
selectReq.InputSerialization.CSV.FileHeaderInfo != CSVFileHeaderInfoIgnore &&
selectReq.InputSerialization.CSV.FileHeaderInfo != "" {
writeErrorResponse(w, ErrInvalidFileHeaderInfo, r.URL)
return
}
if selectReq.OutputSerialization.CSV.QuoteFields != CSVQuoteFieldsAlways &&
selectReq.OutputSerialization.CSV.QuoteFields != CSVQuoteFieldsAsNeeded &&
selectReq.OutputSerialization.CSV.QuoteFields != "" {
writeErrorResponse(w, ErrInvalidQuoteFields, r.URL)
return
}
getObject := objectAPI.GetObject
@ -205,8 +208,7 @@ func (api objectAPIHandlers) SelectObjectContentHandler(w http.ResponseWriter, r
}
go func() {
defer reader.Close()
if gerr := getObject(ctx, bucket, object, 0, objInfo.Size, writer,
objInfo.ETag); gerr != nil {
if gerr := getObject(ctx, bucket, object, 0, objInfo.Size, writer, objInfo.ETag); gerr != nil {
pipewriter.CloseWithError(gerr)
return
}
@ -243,10 +245,9 @@ func (api objectAPIHandlers) SelectObjectContentHandler(w http.ResponseWriter, r
writeErrorResponse(w, toAPIErrorCode(err), r.URL)
return
}
if err := s3s.Execute(w); err != nil {
if err = s3s.Execute(w); err != nil {
logger.LogIf(ctx, err)
}
return
}
}

@ -0,0 +1,89 @@
# Select API Quickstart Guide [![Slack](https://slack.minio.io/slack?type=svg)](https://slack.minio.io)
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.
> This implementation is compatible with AWS S3 Select API
## 1. Prerequisites
- Install Minio Server from [here](http://docs.minio.io/docs/minio-quickstart-guide).
- Familiarity with AWS S3 API
- Familiarity with Python and installing dependencies.
## 2. Install boto3
Install `aws-sdk-python` from AWS SDK for Python official docs [here](https://aws.amazon.com/sdk-for-python/)
## 3. Example
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.
Please replace ``endpoint_url``,``aws_access_key_id``, ``aws_secret_access_key``, ``Bucket`` and ``Key`` with your local setup in this ``select.py`` file.
```py
#!/usr/bin/env/env python3
import boto3
s3 = boto3.client('s3',
endpoint_url='http://localhost:9000',
aws_access_key_id='minio',
aws_secret_access_key='minio123',
region_name='us-east-1')
r = s3.select_object_content(
Bucket='mycsvbucket',
Key='sampledata/TotalPopulation.csv.gz',
ExpressionType='SQL',
Expression="select * from s3object s where s.Location like '%United States%'",
InputSerialization={
'CSV': {
"FileHeaderInfo": "USE",
},
'CompressionType': 'GZIP',
},
OutputSerialization={'CSV': {}},
)
for event in r['Payload']:
if 'Records' in event:
records = event['Records']['Payload'].decode('utf-8')
print(records)
elif 'Stats' in event:
statsDetails = event['Stats']['Details']
print("Stats details bytesScanned: ")
print(statsDetails['BytesScanned'])
print("Stats details bytesProcessed: ")
print(statsDetails['BytesProcessed'])
```
## 4. Run the Program
Upload first a sample dataset downloaded from [TotalPopulation.csv](https://esa.un.org/unpd/wpp/DVD/Files/1_Indicators%20(Standard)/CSV_FILES/WPP2017_TotalPopulationBySex.csv) using the following commands.
```sh
$ curl "https://esa.un.org/unpd/wpp/DVD/Files/1_Indicators%20(Standard)/CSV_FILES/WPP2017_TotalPopulationBySex.csv" > TotalPopulation.csv
$ mc mb myminio/mycsvbucket
$ gzip TotalPopulation.csv
$ mc cp TotalPopulation.csv.gz myminio/mycsvbucket/sampledata/
```
Now let us proceed to run our select example to query for `Location` which matches `United States`.
```sh
$ python3 select.py
840,United States of America,2,Medium,1950,1950.5,79233.218,79571.179,158804.395
840,United States of America,2,Medium,1951,1951.5,80178.933,80726.116,160905.035
840,United States of America,2,Medium,1952,1952.5,81305.206,82019.632,163324.851
840,United States of America,2,Medium,1953,1953.5,82565.875,83422.307,165988.190
....
....
....
Stats details bytesScanned:
6758866
Stats details bytesProcessed:
25786743
```
## 5. Explore Further
- [Use `mc` with Minio Server](https://docs.minio.io/docs/minio-client-quickstart-guide)
- [Use `minio-go` SDK with Minio Server](https://docs.minio.io/docs/golang-client-quickstart-guide)
- [Use `aws-cli` with Minio Server](https://docs.minio.io/docs/aws-cli-with-minio)
- [Use `s3cmd` with Minio Server](https://docs.minio.io/docs/s3cmd-with-minio)
- [The Minio documentation website](https://docs.minio.io)

@ -0,0 +1,33 @@
#!/usr/bin/env/env python3
import boto3
s3 = boto3.client('s3',
endpoint_url='http://localhost:9000',
aws_access_key_id='minio',
aws_secret_access_key='minio123',
region_name='us-east-1')
r = s3.select_object_content(
Bucket='mycsvbucket',
Key='sampledata/TotalPopulation.csv.gz',
ExpressionType='SQL',
Expression="select * from s3object s where s.Location like '%United States%'",
InputSerialization={
'CSV': {
"FileHeaderInfo": "USE",
},
'CompressionType': 'GZIP',
},
OutputSerialization={'CSV': {}},
)
for event in r['Payload']:
if 'Records' in event:
records = event['Records']['Payload'].decode('utf-8')
print(records)
elif 'Stats' in event:
statsDetails = event['Stats']['Details']
print("Stats details bytesScanned: ")
print(statsDetails['BytesScanned'])
print("Stats details bytesProcessed: ")
print(statsDetails['BytesProcessed'])

@ -25,6 +25,9 @@ import (
"github.com/xwb1989/sqlparser"
)
// MaxExpressionLength - 256KiB
const MaxExpressionLength = 256 * 1024
// This function processes size so that we can calculate bytes BytesProcessed.
func processSize(myrecord []string) int64 {
if len(myrecord) > 0 {

Loading…
Cancel
Save