feat: warn when LIKE/ILIKE is used without any %/_ (#9098)

* feat: warn when LIKE/ILIKE is used without any %/_

Signed-off-by: “niladrix719” <niladrix719@gmail.com>

pkg/querybuilder/where_clause_visitor.go

@@ -18,6 +18,8 @@ import (
 
 var searchTroubleshootingGuideURL = "https://signoz.io/docs/userguide/search-troubleshooting/"
 
+const stringMatchingOperatorDocURL = "https://signoz.io/docs/userguide/operators-reference/#string-matching-operators"
+
 // filterExpressionVisitor implements the FilterQueryVisitor interface
 // to convert the parsed filter expressions into ClickHouse WHERE clause
 type filterExpressionVisitor struct {
@@ -533,11 +535,13 @@ func (v *filterExpressionVisitor) VisitComparison(ctx *grammar.ComparisonContext
 			if ctx.NOT() != nil {
 				op = qbtypes.FilterOperatorNotLike
 			}
+			v.warnIfLikeWithoutWildcards("LIKE", value)
 		} else if ctx.ILIKE() != nil {
 			op = qbtypes.FilterOperatorILike
 			if ctx.NOT() != nil {
 				op = qbtypes.FilterOperatorNotILike
 			}
+			v.warnIfLikeWithoutWildcards("ILIKE", value)
 		} else if ctx.REGEXP() != nil {
 			op = qbtypes.FilterOperatorRegexp
 			if ctx.NOT() != nil {
@@ -571,6 +575,19 @@ func (v *filterExpressionVisitor) VisitComparison(ctx *grammar.ComparisonContext
 	return "" // Should not happen with valid input
 }
 
+// warnIfLikeWithoutWildcards adds a guidance warning when LIKE/ILIKE is used without wildcards
+func (v *filterExpressionVisitor) warnIfLikeWithoutWildcards(op string, value any) {
+	if hasLikeWildcards(value) {
+		return
+	}
+
+	msg := op + " operator used without wildcards (% or _). Consider using = operator for exact matches or add wildcards for pattern matching."
+	v.warnings = append(v.warnings, msg)
+	if v.mainWarnURL == "" {
+		v.mainWarnURL = stringMatchingOperatorDocURL
+	}
+}
+
 // VisitInClause handles IN expressions
 func (v *filterExpressionVisitor) VisitInClause(ctx *grammar.InClauseContext) any {
 	if ctx.ValueList() != nil {
@@ -871,6 +888,15 @@ func (v *filterExpressionVisitor) VisitKey(ctx *grammar.KeyContext) any {
 	return fieldKeysForName
 }
 
+// hasLikeWildcards checks if a value contains LIKE wildcards (% or _)
+func hasLikeWildcards(value any) bool {
+	str, ok := value.(string)
+	if !ok {
+		return false
+	}
+	return strings.Contains(str, "%") || strings.Contains(str, "_")
+}
+
 func trimQuotes(txt string) string {
 	if len(txt) >= 2 {
 		if (txt[0] == '"' && txt[len(txt)-1] == '"') ||

pkg/telemetrylogs/filter_expr_like_warning_test.go

@@ -0,0 +1,82 @@
+package telemetrylogs
+
+import (
+	"testing"
+
+	"github.com/SigNoz/signoz/pkg/instrumentation/instrumentationtest"
+	"github.com/SigNoz/signoz/pkg/querybuilder"
+	"github.com/stretchr/testify/require"
+)
+
+// TestLikeAndILikeWithoutWildcards_Warns Tests that LIKE/ILIKE without wildcards add warnings and include docs URL
+func TestLikeAndILikeWithoutWildcards_Warns(t *testing.T) {
+	fm := NewFieldMapper()
+	cb := NewConditionBuilder(fm)
+
+	keys := buildCompleteFieldKeyMap()
+
+	opts := querybuilder.FilterExprVisitorOpts{
+		Logger:           instrumentationtest.New().Logger(),
+		FieldMapper:      fm,
+		ConditionBuilder: cb,
+		FieldKeys:        keys,
+		FullTextColumn:   DefaultFullTextColumn,
+		JsonBodyPrefix:   BodyJSONStringSearchPrefix,
+		JsonKeyToKey:     GetBodyJSONKey,
+	}
+
+	tests := []string{
+		"service.name LIKE 'demo-backend'",
+		"service.name ILIKE 'demo-backend'",
+		"service.name NOT LIKE 'demo-backend'",
+		"service.name NOT ILIKE 'demo-backend'",
+	}
+
+	for _, expr := range tests {
+		t.Run(expr, func(t *testing.T) {
+			clause, err := querybuilder.PrepareWhereClause(expr, opts)
+			require.NoError(t, err)
+			require.NotNil(t, clause)
+
+			require.NotEmpty(t, clause.Warnings, "expected warning for: %s", expr)
+			require.Contains(t, clause.Warnings[0], "operator used without wildcards")
+			require.Contains(t, clause.WarningsDocURL, "operators-reference/#string-matching-operators")
+		})
+	}
+}
+
+// TestLikeAndILikeWithWildcards_NoWarn Tests that LIKE/ILIKE with wildcards do not add warnings
+func TestLikeAndILikeWithWildcards_NoWarn(t *testing.T) {
+	fm := NewFieldMapper()
+	cb := NewConditionBuilder(fm)
+
+	keys := buildCompleteFieldKeyMap()
+
+	opts := querybuilder.FilterExprVisitorOpts{
+		Logger:           instrumentationtest.New().Logger(),
+		FieldMapper:      fm,
+		ConditionBuilder: cb,
+		FieldKeys:        keys,
+		FullTextColumn:   DefaultFullTextColumn,
+		JsonBodyPrefix:   BodyJSONStringSearchPrefix,
+		JsonKeyToKey:     GetBodyJSONKey,
+	}
+
+	tests := []string{
+		"service.name LIKE 'demo-%'",
+		"service.name LIKE '%demo'",
+		"service.name ILIKE '_demo'",
+		"service.name ILIKE '%demo%'",
+	}
+
+	for _, expr := range tests {
+		t.Run(expr, func(t *testing.T) {
+			clause, err := querybuilder.PrepareWhereClause(expr, opts)
+			require.NoError(t, err)
+			require.NotNil(t, clause)
+
+			require.Empty(t, clause.Warnings, "did not expect warnings for: %s", expr)
+			require.Empty(t, clause.WarningsDocURL)
+		})
+	}
+}