go-exasol-client

A simple Go library for connecting to Exasol

This is based on the Exasol websocket API so it requires Exasol versions 6.0 and above.

Examples

import "github.com/grantstreetgroup/go-exasol-client"

func main() {
    conf := exasol.ConnConf{
        Host:     "cluster-node", // IP ranges not yet supported
        Port:     8563,
        Username: "user",
        Password: "pass",
    }
    conn = exasol.Connect(conf)
    defer conn.Disconnect()

    conn.DisableAutoCommit()

    conn.Execute("ALTER SESSION SET...")

    _, err := conn.Execute("INSERT INTO t VALUES(?,?,?)", [][]interface{}{...})

    res, err := conn.FetchSlice("SELECT * FROM t WHERE c = ?", []interface{}{...})
    for _, row := range res {
        col = row[0].(string)
    }

    // For large datasets use FetchChan to avoid buffering
    // the entire resultset in memory
    res, err = conn.FetchChan("SELECT * FROM t")
    for row := range res {
        col = row[0].(string)
    }


    // For very large datasets you can send/receive your data
    // in CSV format (stored in a bytes.Buffer) using the Bulk* methods.
    // This is the fastest way to upload or download data to Exasol.
    var csvData new(bytes.Buffer)
    csvData.WriteString("csv,data,...\n...")

    // To upload to a particular table
    err = conn.BulkInsert(schemaName, tableName, csvData)

    // To select all data from a particular table
    err = conn.BulkSelect(schemaName, tableName, csvData)
    SomeCSVParser(csvData.String())

    // To select an arbitrary query
    sql := "EXPORT (SELECT c FROM t) INTO CSV AT '%%s' FILE 'data.csv'"
    err = conn.BulkQuery(sql, csvData)
    SomeCSVParser(csvData.String())


    // For extremely large datasets that cannot fit in memory
    // You can stream your CSV data to/from any of the above Bulk methods
    // by using the equivalent Stream... method.
    // The stream consists of a chan of byte slices where each byte
    // slice is optimally around 8K in size
    csvChan := make(chan []byte, 1000) // Chan size depends on your memory
    go func {
        for {
            ...
            // Generate your CSV data in ~8K chunks
            csvChan <- []byte("csv,data...\n...")
        }
        close(csvChan)
    }
    err := conn.StreamInsert(schemaName, tableName, csvChan)


    go func {
        // Read your CSV data in ~8K chunks
        for chunk := range csvChan {
            // chunk is a []byte with partial csvData
        }
    }
    bytesRead, err := conn.StreamSelect(schemaName, tableName, csvChan)


    conn.Commit()
}

TODOs

• This library needs to be adapted to the standard Go database/sql interface.
• Add support for cluster node IP address ranges
• Add support encryption and compression
• Implement timeouts for all query types
• Add tests

Author

Grant Street Group [email protected]

Copyright and License

This software is Copyright (c) 2019 by Grant Street Group.

This is free software, licensed under:

MIT License

Contributors

• Peter Kioko [email protected]