Merge pull request #11 from agoncear-mwb/main

Added explicit key for using unsafe string reader

Author: auxten

chdb/driver/driver.go

@@ -25,12 +25,14 @@ const (
 	INVALID
 )
 
-const sessionOptionKey = "session"
-const udfPathOptionKey = "udfPath"
-const driverTypeKey = "driverType"
-const driverBufferSizeKey = "bufferSize"
-
-const defaultBufferSize = 512
+const (
+	sessionOptionKey         = "session"
+	udfPathOptionKey         = "udfPath"
+	driverTypeKey            = "driverType"
+	useUnsafeStringReaderKey = "useUnsafeStringReader"
+	driverBufferSizeKey      = "bufferSize"
+	defaultBufferSize        = 512
+)
 
 func (d DriverType) String() string {
 	switch d {
@@ -44,7 +46,7 @@ func (d DriverType) String() string {
 	return ""
 }
 
-func (d DriverType) PrepareRows(result *chdbstable.LocalResult, buf []byte, bufSize int) (driver.Rows, error) {
+func (d DriverType) PrepareRows(result *chdbstable.LocalResult, buf []byte, bufSize int, useUnsafe bool) (driver.Rows, error) {
 	switch d {
 	case ARROW:
 		reader, err := ipc.NewFileReader(bytes.NewReader(buf))
@@ -54,7 +56,11 @@ func (d DriverType) PrepareRows(result *chdbstable.LocalResult, buf []byte, bufS
 		return &arrowRows{localResult: result, reader: reader}, nil
 	case PARQUET:
 		reader := parquet.NewGenericReader[any](bytes.NewReader(buf))
-		return &parquetRows{localResult: result, reader: reader, bufferSize: bufSize, needNewBuffer: true}, nil
+		return &parquetRows{
+			localResult: result, reader: reader,
+			bufferSize: bufSize, needNewBuffer: true,
+			useUnsafeStringReader: useUnsafe,
+		}, nil
 	}
 	return nil, fmt.Errorf("Unsupported driver type")
 }
@@ -79,6 +85,7 @@ type connector struct {
 	udfPath    string
 	driverType DriverType
 	bufferSize int
+	useUnsafe  bool
 	session    *chdb.Session
 }
 
@@ -87,7 +94,11 @@ func (c *connector) Connect(ctx context.Context) (driver.Conn, error) {
 	if c.driverType == INVALID {
 		return nil, fmt.Errorf("DriverType not supported")
 	}
-	cc := &conn{udfPath: c.udfPath, session: c.session, driverType: c.driverType, bufferSize: c.bufferSize}
+	cc := &conn{
+		udfPath: c.udfPath, session: c.session,
+		driverType: c.driverType, bufferSize: c.bufferSize,
+		useUnsafe: c.useUnsafe,
+	}
 	cc.SetupQueryFun()
 	return cc, nil
 }
@@ -138,6 +149,12 @@ func NewConnect(opts map[string]string) (ret *connector, err error) {
 	} else {
 		ret.bufferSize = defaultBufferSize
 	}
+	useUnsafe, ok := opts[useUnsafeStringReaderKey]
+	if ok {
+		if strings.ToLower(useUnsafe) == "true" {
+			ret.useUnsafe = true
+		}
+	}
 
 	udfPath, ok := opts[udfPathOptionKey]
 	if ok {
@@ -170,6 +187,7 @@ type conn struct {
 	udfPath    string
 	driverType DriverType
 	bufferSize int
+	useUnsafe  bool
 	session    *chdb.Session
 	QueryFun   queryHandle
 }
@@ -229,7 +247,7 @@ func (c *conn) QueryContext(ctx context.Context, query string, args []driver.Nam
 	if buf == nil {
 		return nil, fmt.Errorf("result is nil")
 	}
-	return c.driverType.PrepareRows(result, buf, c.bufferSize)
+	return c.driverType.PrepareRows(result, buf, c.bufferSize, c.useUnsafe)
 
 }
 

chdb/driver/parquet.go

@@ -13,6 +13,8 @@ import (
 	"github.com/parquet-go/parquet-go"
 )
 
+// NOTE: this function is strictly unsafe and can lead to undefined behavior if the underlying slice is going out of scope or if it is being modified while in use.
+// Use this function ONLY if you know that both of the conditions are respected and you need to allocate less memory possible.
 func bytesToString(data []byte) string {
 	return *(*string)(unsafe.Pointer(&data))
 }
@@ -22,14 +24,15 @@ func getStringFromBytes(v parquet.Value) string {
 }
 
 type parquetRows struct {
-	localResult   *chdbstable.LocalResult     // result from clickhouse
-	reader        *parquet.GenericReader[any] // parquet reader
-	curRecord     parquet.Row                 // TODO: delete this?
-	buffer        []parquet.Row               // record buffer
-	bufferSize    int                         // amount of records to preload into buffer
-	bufferIndex   int64                       // index in the current buffer
-	curRow        int64                       // row counter
-	needNewBuffer bool
+	localResult           *chdbstable.LocalResult     // result from clickhouse
+	reader                *parquet.GenericReader[any] // parquet reader
+	curRecord             parquet.Row                 // TODO: delete this?
+	buffer                []parquet.Row               // record buffer
+	bufferSize            int                         // amount of records to preload into buffer
+	bufferIndex           int64                       // index in the current buffer
+	curRow                int64                       // row counter
+	needNewBuffer         bool
+	useUnsafeStringReader bool
 }
 
 func (r *parquetRows) Columns() (out []string) {
@@ -100,7 +103,14 @@ func (r *parquetRows) Next(dest []driver.Value) error {
 		}
 		switch r.ColumnTypeDatabaseTypeName(columnIndex) {
 		case "STRING":
-			dest[columnIndex] = getStringFromBytes(curVal)
+			// we check if the user has initialized the connection with the unsafeStringReader parameter, and in that case we use `getStringFromBytes` method.
+			// otherwise, we fallback to the traditional way and we allocate a new string
+			if r.useUnsafeStringReader {
+				dest[columnIndex] = getStringFromBytes(curVal)
+			} else {
+				dest[columnIndex] = string(curVal.ByteArray())
+			}
+
 		case "INT8", "INT(8,true)":
 			dest[columnIndex] = int8(curVal.Int32()) //check if this is correct
 		case "INT16", "INT(16,true)":