csvq

csvq driver

A go database/sql driver for csvq.

csvq-driver allows you to operate csv files and other supported formats using csvq statements in Go. You can use the statements in the same way as other relational database systems.

Reference Manual - csvq

Requirements

Go 1.14 or later (ref. Getting Started - The Go Programming Language)

Supported features

• Query
  • Only the result-sets in the top-level scope can be retrieved. You cannot refer the results of child scopes such as inside of IF, WHILE and user-defined functions.
• Exec
  • Only the last result in the top-level scope can be retrieved.
  • LastInsertId is not supported.
• Prepared Statement
  • Ordinal placeholders
  • Named placeholders
• Transaction
  • Isolation Level is the default only.
  • Read-only transaction is not supported.
  • If you do not use the database/sql transaction feature, all execusions will commit at the end of the execusion automatically.

Usage

Data Source Name

A data source name to call sql.Open is a directory path. It is the same as "--repository" option of the csvq command.

Some parameters can be specified in a DSN string with a directory path. A directory path and parameters are separated by a question mark, and parameters are separated by ampersands.

db, err := sql.Open("csvq", "/path/to/data/directory?Param1=Value&Param2=Value")

Parameters that can be specified

Parameter names are case-insensitive.

See: csvq > Reference Manual > Command Usage > Options

Error Handling

If a received error is a returned error from csvq, you can cast the error to github.com/mithrandie/csvq/lib/query.Error interface. The error interface has following functions.

Example

package main

import (
	"context"
	"database/sql"
	"fmt"

	"github.com/mithrandie/csvq/lib/query"

	_ "github.com/mithrandie/csvq-driver"
)

func main() {
	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()

	db, err := sql.Open("csvq", "/path/to/data/directory")
	if err != nil {
		panic(err)
	}
	defer func() {
		if err := db.Close(); err != nil {
			panic(err)
		}
	}()
	
	queryString := "SELECT id, first_name, country_code FROM `users.csv` WHERE id = '12'"
	r := db.QueryRowContext(ctx, queryString)

	var (
		id          int
		firstName   string
		countryCode string
	)

	if err := r.Scan(&id, &firstName, &countryCode); err != nil {
		if err == sql.ErrNoRows {
			fmt.Println("No Rows.")
		} else if csvqerr, ok := err.(query.Error); ok {
			panic(fmt.Sprintf("Unexpected error: Number: %d  Message: %s", csvqerr.Number(), csvqerr.Message()))
		} else {
			panic("Unexpected error: " + err.Error())
		}
	} else {
		fmt.Printf("Result: [id]%3d  [first_name]%10s  [country_code]%3s\n", id, firstName, countryCode)
	}
}

See: https://github.com/mithrandie/csvq-driver/blob/master/example/csvq-driver/csvq-driver-example.go

Replace I/O

You can replace input/output interface of the csvq to pass the data from inside of your go programs or retrive the result-sets as a another format.

The following structs are available for replacement.

"query" means the package "github.com/mithrandie/csvq/lib/query".

See: https://github.com/mithrandie/csvq-driver/blob/master/example/replace-io/csvq-replace-io-example.go