1 files changed, 354 insertions, 0 deletions
diff --git a/weed/query/engine/string_functions.go b/weed/query/engine/string_functions.go
new file mode 100644
index 000000000..2143a75bc
--- /dev/null
+++ b/weed/query/engine/string_functions.go
@@ -0,0 +1,354 @@
+package engine
+
+import (
+	"fmt"
+	"math"
+	"strings"
+
+	"github.com/seaweedfs/seaweedfs/weed/pb/schema_pb"
+)
+
+// ===============================
+// STRING FUNCTIONS
+// ===============================
+
+// Length returns the length of a string
+func (e *SQLEngine) Length(value *schema_pb.Value) (*schema_pb.Value, error) {
+	if value == nil {
+		return nil, fmt.Errorf("LENGTH function requires non-null value")
+	}
+
+	str, err := e.valueToString(value)
+	if err != nil {
+		return nil, fmt.Errorf("LENGTH function conversion error: %v", err)
+	}
+
+	length := int64(len(str))
+	return &schema_pb.Value{
+		Kind: &schema_pb.Value_Int64Value{Int64Value: length},
+	}, nil
+}
+
+// Upper converts a string to uppercase
+func (e *SQLEngine) Upper(value *schema_pb.Value) (*schema_pb.Value, error) {
+	if value == nil {
+		return nil, fmt.Errorf("UPPER function requires non-null value")
+	}
+
+	str, err := e.valueToString(value)
+	if err != nil {
+		return nil, fmt.Errorf("UPPER function conversion error: %v", err)
+	}
+
+	return &schema_pb.Value{
+		Kind: &schema_pb.Value_StringValue{StringValue: strings.ToUpper(str)},
+	}, nil
+}
+
+// Lower converts a string to lowercase
+func (e *SQLEngine) Lower(value *schema_pb.Value) (*schema_pb.Value, error) {
+	if value == nil {
+		return nil, fmt.Errorf("LOWER function requires non-null value")
+	}
+
+	str, err := e.valueToString(value)
+	if err != nil {
+		return nil, fmt.Errorf("LOWER function conversion error: %v", err)
+	}
+
+	return &schema_pb.Value{
+		Kind: &schema_pb.Value_StringValue{StringValue: strings.ToLower(str)},
+	}, nil
+}
+
+// Trim removes leading and trailing whitespace from a string
+func (e *SQLEngine) Trim(value *schema_pb.Value) (*schema_pb.Value, error) {
+	if value == nil {
+		return nil, fmt.Errorf("TRIM function requires non-null value")
+	}
+
+	str, err := e.valueToString(value)
+	if err != nil {
+		return nil, fmt.Errorf("TRIM function conversion error: %v", err)
+	}
+
+	return &schema_pb.Value{
+		Kind: &schema_pb.Value_StringValue{StringValue: strings.TrimSpace(str)},
+	}, nil
+}
+
+// LTrim removes leading whitespace from a string
+func (e *SQLEngine) LTrim(value *schema_pb.Value) (*schema_pb.Value, error) {
+	if value == nil {
+		return nil, fmt.Errorf("LTRIM function requires non-null value")
+	}
+
+	str, err := e.valueToString(value)
+	if err != nil {
+		return nil, fmt.Errorf("LTRIM function conversion error: %v", err)
+	}
+
+	return &schema_pb.Value{
+		Kind: &schema_pb.Value_StringValue{StringValue: strings.TrimLeft(str, " \t\n\r")},
+	}, nil
+}
+
+// RTrim removes trailing whitespace from a string
+func (e *SQLEngine) RTrim(value *schema_pb.Value) (*schema_pb.Value, error) {
+	if value == nil {
+		return nil, fmt.Errorf("RTRIM function requires non-null value")
+	}
+
+	str, err := e.valueToString(value)
+	if err != nil {
+		return nil, fmt.Errorf("RTRIM function conversion error: %v", err)
+	}
+
+	return &schema_pb.Value{
+		Kind: &schema_pb.Value_StringValue{StringValue: strings.TrimRight(str, " \t\n\r")},
+	}, nil
+}
+
+// Substring extracts a substring from a string
+func (e *SQLEngine) Substring(value *schema_pb.Value, start *schema_pb.Value, length ...*schema_pb.Value) (*schema_pb.Value, error) {
+	if value == nil || start == nil {
+		return nil, fmt.Errorf("SUBSTRING function requires non-null value and start position")
+	}
+
+	str, err := e.valueToString(value)
+	if err != nil {
+		return nil, fmt.Errorf("SUBSTRING function value conversion error: %v", err)
+	}
+
+	startPos, err := e.valueToInt64(start)
+	if err != nil {
+		return nil, fmt.Errorf("SUBSTRING function start position conversion error: %v", err)
+	}
+
+	// Convert to 0-based indexing (SQL uses 1-based)
+	if startPos < 1 {
+		startPos = 1
+	}
+	startIdx := int(startPos - 1)
+
+	if startIdx >= len(str) {
+		return &schema_pb.Value{
+			Kind: &schema_pb.Value_StringValue{StringValue: ""},
+		}, nil
+	}
+
+	var result string
+	if len(length) > 0 && length[0] != nil {
+		lengthVal, err := e.valueToInt64(length[0])
+		if err != nil {
+			return nil, fmt.Errorf("SUBSTRING function length conversion error: %v", err)
+		}
+
+		if lengthVal <= 0 {
+			result = ""
+		} else {
+			if lengthVal > int64(math.MaxInt) || lengthVal < int64(math.MinInt) {
+				// If length is out-of-bounds for int, take substring from startIdx to end
+				result = str[startIdx:]
+			} else {
+				// Safe conversion after bounds check
+				endIdx := startIdx + int(lengthVal)
+				if endIdx > len(str) {
+					endIdx = len(str)
+				}
+				result = str[startIdx:endIdx]
+			}
+		}
+	} else {
+		result = str[startIdx:]
+	}
+
+	return &schema_pb.Value{
+		Kind: &schema_pb.Value_StringValue{StringValue: result},
+	}, nil
+}
+
+// Concat concatenates multiple strings
+func (e *SQLEngine) Concat(values ...*schema_pb.Value) (*schema_pb.Value, error) {
+	if len(values) == 0 {
+		return &schema_pb.Value{
+			Kind: &schema_pb.Value_StringValue{StringValue: ""},
+		}, nil
+	}
+
+	var result strings.Builder
+	for i, value := range values {
+		if value == nil {
+			continue // Skip null values
+		}
+
+		str, err := e.valueToString(value)
+		if err != nil {
+			return nil, fmt.Errorf("CONCAT function value %d conversion error: %v", i, err)
+		}
+		result.WriteString(str)
+	}
+
+	return &schema_pb.Value{
+		Kind: &schema_pb.Value_StringValue{StringValue: result.String()},
+	}, nil
+}
+
+// Replace replaces all occurrences of a substring with another substring
+func (e *SQLEngine) Replace(value, oldStr, newStr *schema_pb.Value) (*schema_pb.Value, error) {
+	if value == nil || oldStr == nil || newStr == nil {
+		return nil, fmt.Errorf("REPLACE function requires non-null values")
+	}
+
+	str, err := e.valueToString(value)
+	if err != nil {
+		return nil, fmt.Errorf("REPLACE function value conversion error: %v", err)
+	}
+
+	old, err := e.valueToString(oldStr)
+	if err != nil {
+		return nil, fmt.Errorf("REPLACE function old string conversion error: %v", err)
+	}
+
+	new, err := e.valueToString(newStr)
+	if err != nil {
+		return nil, fmt.Errorf("REPLACE function new string conversion error: %v", err)
+	}
+
+	result := strings.ReplaceAll(str, old, new)
+
+	return &schema_pb.Value{
+		Kind: &schema_pb.Value_StringValue{StringValue: result},
+	}, nil
+}
+
+// Position returns the position of a substring in a string (1-based, 0 if not found)
+func (e *SQLEngine) Position(substring, value *schema_pb.Value) (*schema_pb.Value, error) {
+	if substring == nil || value == nil {
+		return nil, fmt.Errorf("POSITION function requires non-null values")
+	}
+
+	str, err := e.valueToString(value)
+	if err != nil {
+		return nil, fmt.Errorf("POSITION function string conversion error: %v", err)
+	}
+
+	substr, err := e.valueToString(substring)
+	if err != nil {
+		return nil, fmt.Errorf("POSITION function substring conversion error: %v", err)
+	}
+
+	pos := strings.Index(str, substr)
+	if pos == -1 {
+		pos = 0 // SQL returns 0 for not found
+	} else {
+		pos = pos + 1 // Convert to 1-based indexing
+	}
+
+	return &schema_pb.Value{
+		Kind: &schema_pb.Value_Int64Value{Int64Value: int64(pos)},
+	}, nil
+}
+
+// Left returns the leftmost characters of a string
+func (e *SQLEngine) Left(value *schema_pb.Value, length *schema_pb.Value) (*schema_pb.Value, error) {
+	if value == nil || length == nil {
+		return nil, fmt.Errorf("LEFT function requires non-null values")
+	}
+
+	str, err := e.valueToString(value)
+	if err != nil {
+		return nil, fmt.Errorf("LEFT function string conversion error: %v", err)
+	}
+
+	lengthVal, err := e.valueToInt64(length)
+	if err != nil {
+		return nil, fmt.Errorf("LEFT function length conversion error: %v", err)
+	}
+
+	if lengthVal <= 0 {
+		return &schema_pb.Value{
+			Kind: &schema_pb.Value_StringValue{StringValue: ""},
+		}, nil
+	}
+
+	if lengthVal > int64(len(str)) {
+		return &schema_pb.Value{
+			Kind: &schema_pb.Value_StringValue{StringValue: str},
+		}, nil
+	}
+
+	if lengthVal > int64(math.MaxInt) || lengthVal < int64(math.MinInt) {
+		return &schema_pb.Value{
+			Kind: &schema_pb.Value_StringValue{StringValue: str},
+		}, nil
+	}
+
+	// Safe conversion after bounds check
+	return &schema_pb.Value{
+		Kind: &schema_pb.Value_StringValue{StringValue: str[:int(lengthVal)]},
+	}, nil
+}
+
+// Right returns the rightmost characters of a string
+func (e *SQLEngine) Right(value *schema_pb.Value, length *schema_pb.Value) (*schema_pb.Value, error) {
+	if value == nil || length == nil {
+		return nil, fmt.Errorf("RIGHT function requires non-null values")
+	}
+
+	str, err := e.valueToString(value)
+	if err != nil {
+		return nil, fmt.Errorf("RIGHT function string conversion error: %v", err)
+	}
+
+	lengthVal, err := e.valueToInt64(length)
+	if err != nil {
+		return nil, fmt.Errorf("RIGHT function length conversion error: %v", err)
+	}
+
+	if lengthVal <= 0 {
+		return &schema_pb.Value{
+			Kind: &schema_pb.Value_StringValue{StringValue: ""},
+		}, nil
+	}
+
+	if lengthVal > int64(len(str)) {
+		return &schema_pb.Value{
+			Kind: &schema_pb.Value_StringValue{StringValue: str},
+		}, nil
+	}
+
+	if lengthVal > int64(math.MaxInt) || lengthVal < int64(math.MinInt) {
+		return &schema_pb.Value{
+			Kind: &schema_pb.Value_StringValue{StringValue: str},
+		}, nil
+	}
+
+	// Safe conversion after bounds check
+	startPos := len(str) - int(lengthVal)
+	return &schema_pb.Value{
+		Kind: &schema_pb.Value_StringValue{StringValue: str[startPos:]},
+	}, nil
+}
+
+// Reverse reverses a string
+func (e *SQLEngine) Reverse(value *schema_pb.Value) (*schema_pb.Value, error) {
+	if value == nil {
+		return nil, fmt.Errorf("REVERSE function requires non-null value")
+	}
+
+	str, err := e.valueToString(value)
+	if err != nil {
+		return nil, fmt.Errorf("REVERSE function conversion error: %v", err)
+	}
+
+	// Reverse the string rune by rune to handle Unicode correctly
+	runes := []rune(str)
+	for i, j := 0, len(runes)-1; i < j; i, j = i+1, j-1 {
+		runes[i], runes[j] = runes[j], runes[i]
+	}
+
+	return &schema_pb.Value{
+		Kind: &schema_pb.Value_StringValue{StringValue: string(runes)},
+	}, nil
+}