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snowflake.go
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snowflake.go
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package sql
import (
"database/sql"
"strconv"
"time"
"github.com/influxdata/flux"
"github.com/influxdata/flux/codes"
"github.com/influxdata/flux/execute"
"github.com/influxdata/flux/internal/errors"
"github.com/influxdata/flux/values"
)
// Snowflake DB support.
// Notes:
// * type mapping
// - see https://pkg.go.dev/github.com/snowflakedb/gosnowflake
// - current mappings are valid for v1.3.4
type SnowflakeRowReader struct {
Cursor *sql.Rows
columns []interface{}
columnTypes []flux.ColType
columnNames []string
sqlTypes []*sql.ColumnType
NextFunc func() bool
CloseFunc func() error
}
const (
layoutDate = "2006-01-02"
layoutTime = "15:04:05"
layoutTimeStampNtz = "2006-01-02T15:04:05.0000000000"
)
// Next prepares SnowflakeRowReader to return rows
func (m *SnowflakeRowReader) Next() bool {
if m.NextFunc != nil {
return m.NextFunc()
}
next := m.Cursor.Next()
if next {
columnNames, err := m.Cursor.Columns()
if err != nil {
return false
}
m.columns = make([]interface{}, len(columnNames))
columnPointers := make([]interface{}, len(columnNames))
for i := 0; i < len(columnNames); i++ {
columnPointers[i] = &m.columns[i]
}
if err := m.Cursor.Scan(columnPointers...); err != nil {
return false
}
}
return next
}
func (m *SnowflakeRowReader) GetNextRow() ([]values.Value, error) {
row := make([]values.Value, len(m.columns))
for i, column := range m.columns {
switch value := column.(type) {
case bool, int64, float64: // never happens with scan into []*interface{}
row[i] = values.New(value)
case string:
switch m.columnTypes[i] {
case flux.TFloat:
f, err := strconv.ParseFloat(value, 64)
if err != nil {
return nil, err
}
row[i] = values.NewFloat(f)
case flux.TInt:
d, err := strconv.ParseInt(value, 10, 64)
if err != nil {
return nil, err
}
row[i] = values.NewInt(d)
case flux.TBool:
b, err := strconv.ParseBool(value)
if err != nil {
return nil, err
}
row[i] = values.NewBool(b)
default:
row[i] = values.New(value)
}
case time.Time:
// DATE, TIME and TIMESTAMP_NTZ types get scanned to time.Time by the driver,
// but they have no counterpart in Flux therefore will be represented as string
switch m.sqlTypes[i].DatabaseTypeName() {
case "DATE":
row[i] = values.NewString(value.Format(layoutDate))
case "TIME":
row[i] = values.NewString(value.Format(layoutTime))
case "TIMESTAMP_NTZ":
row[i] = values.NewString(value.Format(layoutTimeStampNtz))
default:
row[i] = values.NewTime(values.ConvertTime(value))
}
case nil:
row[i] = values.NewNull(flux.SemanticType(m.columnTypes[i]))
default:
execute.PanicUnknownType(flux.TInvalid)
}
}
return row, nil
}
func (m *SnowflakeRowReader) InitColumnNames(names []string) {
m.columnNames = names
}
func (m *SnowflakeRowReader) InitColumnTypes(types []*sql.ColumnType) {
fluxTypes := make([]flux.ColType, len(types))
for i := 0; i < len(types); i++ {
switch types[i].DatabaseTypeName() {
case "FIXED", "NUMBER": // FIXED is reported by Snowflake driver
_, scale, ok := types[i].DecimalSize()
if ok && scale > 0 {
fluxTypes[i] = flux.TFloat
} else {
fluxTypes[i] = flux.TInt
}
case "REAL", "FLOAT": // REAL is reported by Snowflake driver
fluxTypes[i] = flux.TFloat
case "BOOLEAN":
fluxTypes[i] = flux.TBool
case "TIMESTAMP_TZ", "TIMESTAMP_LTZ": // "TIMESTAMP_NTZ", "DATE" and "TIME" will be represented as string
fluxTypes[i] = flux.TTime
default:
fluxTypes[i] = flux.TString
}
}
m.columnTypes = fluxTypes
m.sqlTypes = types
}
func (m *SnowflakeRowReader) ColumnNames() []string {
return m.columnNames
}
func (m *SnowflakeRowReader) ColumnTypes() []flux.ColType {
return m.columnTypes
}
func (m *SnowflakeRowReader) SetColumnTypes(types []flux.ColType) {
m.columnTypes = types
}
func (m *SnowflakeRowReader) SetColumns(i []interface{}) {
m.columns = i
}
func (m *SnowflakeRowReader) Close() error {
if m.CloseFunc != nil {
return m.CloseFunc()
}
if err := m.Cursor.Err(); err != nil {
return err
}
return m.Cursor.Close()
}
func NewSnowflakeRowReader(r *sql.Rows) (execute.RowReader, error) {
reader := &SnowflakeRowReader{
Cursor: r,
}
cols, err := r.Columns()
if err != nil {
return nil, err
}
reader.InitColumnNames(cols)
types, err := r.ColumnTypes()
if err != nil {
return nil, err
}
reader.InitColumnTypes(types)
return reader, nil
}
var fluxToSnowflake = map[flux.ColType]string{
flux.TFloat: "FLOAT",
flux.TInt: "NUMBER",
flux.TString: "TEXT",
flux.TBool: "BOOLEAN",
flux.TTime: "TIMESTAMP_LTZ",
}
// SnowflakeTranslateColumn translates flux colTypes into their corresponding Snowflake column type
func SnowflakeColumnTranslateFunc() translationFunc {
return func(f flux.ColType, colName string) (string, error) {
s, found := fluxToSnowflake[f]
if !found {
return "", errors.Newf(codes.Internal, "Snowflake does not support column type %s", f.String())
}
return colName + " " + s, nil
}
}