Merge pull request #10 from VictoriaMetrics/json-value

Implement JSON_VALUE function from ANSI SQL (#9)

Author: Amper

README.md

@@ -135,6 +135,7 @@ Supported highlights:
   - arithmetic expressions, 
   - string helpers (`SUBSTR`, `CONCAT`, `TRIM`, `REPLACE`, `LOWER`, `UPPER`), 
   - math (`ABS`, `CEIL`, `FLOOR`, `ROUND`, `LEAST`, `GREATEST`), 
+  - JSON (`JSON_VALUE`),
   - and date helpers (`CURRENT_DATE`, `CURRENT_TIMESTAMP`).
 - `WHERE` with comparison operators, `BETWEEN`, `IN`, `LIKE`, `IS (NOT) NULL`
 - `ORDER BY`, `LIMIT`, `OFFSET`, `DISTINCT`

cmd/sql-to-logsql/web/ui/src/components/docs/Docs.tsx

@@ -82,12 +82,12 @@ export function Docs() {
              <p>
                <ul className={"list-disc pl-4 pt-2"}>
                  <li><code>SUBSTR, CONCAT, LOWER, UPPER, TRIM, LTRIM, RTRIM, REPLACE</code></li>
-                 <li><code>LIKE, NOT LIKE</code></li>
-                 <li><code>BETWEEN</code></li>
+                 <li><code>LIKE, NOT LIKE, =, !=, &lt;, &gt;, &lt;=, &gt;=, BETWEEN</code></li>
                  <li><code>+,-, *, /, %, ^</code></li>
                  <li><code>ABS, GREATEST, LEAST, ROUND, FLOOR, CEIL, POW, LN, EXP</code></li>
                  <li><code>SUM, COUNT, MAX, MIN, AVG</code></li>
                  <li><code>CURRENT_TIMESTAMP, CURREN_DATE</code></li>
+                 <li><code>JSON_VALUE</code></li>
                </ul>
              </p>
            </AccordionContent>

lib/logsql/jsonpath.go

@@ -0,0 +1,210 @@
+package logsql
+
+import (
+	"fmt"
+	"net/http"
+	"strconv"
+	"strings"
+	"unicode"
+)
+
+type jsonPath struct {
+	Strict bool
+	Steps  []jsonPathStep
+}
+
+type jsonPathStep struct {
+	Key   string
+	Index *int
+}
+
+func parseJSONPath(raw string) (*jsonPath, error) {
+	if strings.TrimSpace(raw) == "" {
+		return nil, &TranslationError{
+			Code:    http.StatusBadRequest,
+			Message: "translator: JSON path cannot be empty",
+		}
+	}
+
+	path := strings.TrimSpace(raw)
+	lower := strings.ToLower(path)
+	result := &jsonPath{}
+
+	switch {
+	case strings.HasPrefix(lower, "strict "):
+		result.Strict = true
+		path = strings.TrimSpace(path[len("strict "):])
+	case strings.HasPrefix(lower, "lax "):
+		result.Strict = false
+		path = strings.TrimSpace(path[len("lax "):])
+	}
+
+	if path == "" || path[0] != '$' {
+		return nil, &TranslationError{
+			Code:    http.StatusBadRequest,
+			Message: "translator: JSON path must start with $",
+		}
+	}
+	path = path[1:]
+	runes := []rune(path)
+
+	i := 0
+	for {
+		skipSpaces(runes, &i)
+		if i >= len(runes) {
+			break
+		}
+
+		switch runes[i] {
+		case '.':
+			i++
+			skipSpaces(runes, &i)
+			if i >= len(runes) {
+				return nil, &TranslationError{
+					Code:    http.StatusBadRequest,
+					Message: "translator: JSON path ends unexpectedly after .",
+				}
+			}
+			start := i
+			for i < len(runes) {
+				r := runes[i]
+				if r == '.' || r == '[' {
+					break
+				}
+				i++
+			}
+			if start == i {
+				return nil, &TranslationError{
+					Code:    http.StatusBadRequest,
+					Message: "translator: JSON path contains empty segment",
+				}
+			}
+			key := strings.TrimSpace(string(runes[start:i]))
+			if key == "" {
+				return nil, &TranslationError{
+					Code:    http.StatusBadRequest,
+					Message: "translator: JSON path contains empty segment",
+				}
+			}
+			result.Steps = append(result.Steps, jsonPathStep{Key: key})
+		case '[':
+			i++
+			skipSpaces(runes, &i)
+			if i >= len(runes) {
+				return nil, &TranslationError{
+					Code:    http.StatusBadRequest,
+					Message: "translator: JSON path has unterminated []",
+				}
+			}
+			step, err := parseBracketStep(runes, &i)
+			if err != nil {
+				return nil, err
+			}
+			result.Steps = append(result.Steps, step)
+			skipSpaces(runes, &i)
+			if i >= len(runes) || runes[i] != ']' {
+				return nil, &TranslationError{
+					Code:    http.StatusBadRequest,
+					Message: "translator: JSON path has unterminated []",
+				}
+			}
+			i++
+		default:
+			return nil, &TranslationError{
+				Code:    http.StatusBadRequest,
+				Message: fmt.Sprintf("translator: unsupported JSON path token %q", string(runes[i])),
+			}
+		}
+	}
+
+	if len(result.Steps) == 0 {
+		return nil, &TranslationError{
+			Code:    http.StatusBadRequest,
+			Message: "translator: JSON path must reference nested field",
+		}
+	}
+	return result, nil
+}
+
+func (p *jsonPath) HasOnlyKeys() ([]string, bool) {
+	if p == nil {
+		return nil, false
+	}
+	keys := make([]string, 0, len(p.Steps))
+	for _, step := range p.Steps {
+		if step.Index != nil || step.Key == "" {
+			return nil, false
+		}
+		keys = append(keys, step.Key)
+	}
+	return keys, true
+}
+
+func parseBracketStep(runes []rune, pos *int) (jsonPathStep, error) {
+	if *pos >= len(runes) {
+		return jsonPathStep{}, &TranslationError{
+			Code:    http.StatusBadRequest,
+			Message: "translator: JSON path has unterminated []",
+		}
+	}
+	switch runes[*pos] {
+	case '\'', '"':
+		quote := runes[*pos]
+		*pos++
+		var builder strings.Builder
+		for *pos < len(runes) {
+			r := runes[*pos]
+			*pos++
+			if r == '\\' {
+				if *pos >= len(runes) {
+					return jsonPathStep{}, &TranslationError{
+						Code:    http.StatusBadRequest,
+						Message: "translator: JSON path has invalid escape sequence",
+					}
+				}
+				builder.WriteRune(runes[*pos])
+				*pos++
+				continue
+			}
+			if r == quote {
+				break
+			}
+			builder.WriteRune(r)
+		}
+		key := strings.TrimSpace(builder.String())
+		if key == "" {
+			return jsonPathStep{}, &TranslationError{
+				Code:    http.StatusBadRequest,
+				Message: "translator: JSON path contains empty segment",
+			}
+		}
+		return jsonPathStep{Key: key}, nil
+	default:
+		start := *pos
+		for *pos < len(runes) && unicode.IsDigit(runes[*pos]) {
+			*pos++
+		}
+		if start == *pos {
+			return jsonPathStep{}, &TranslationError{
+				Code:    http.StatusBadRequest,
+				Message: "translator: JSON path contains unsupported token inside []",
+			}
+		}
+		value := string(runes[start:*pos])
+		index, err := strconv.Atoi(value)
+		if err != nil {
+			return jsonPathStep{}, &TranslationError{
+				Code:    http.StatusBadRequest,
+				Message: "translator: JSON path contains unsupported index",
+				Err:     err,
+			}
+		}
+		return jsonPathStep{Index: &index}, nil
+	}
+}
+
+func skipSpaces(runes []rune, pos *int) {
+	for *pos < len(runes) && unicode.IsSpace(runes[*pos]) {
+		*pos++
+	}
+}