SQL Expressions: Rework backend errors and error instrumentation (#109633)

* Capture error_type label on metrics/traces
* Make error messages more helpful to user
* Use errutil, categorized errors, and tie them to error_type (category in code)
* Misc trace fixes
* Add metric to track SQL input conversion

pkg/expr/errors.go

@@ -3,8 +3,6 @@ package expr
 import (
 	"errors"
 	"fmt"
-	"sort"
-	"strings"
 
 	"github.com/grafana/grafana/pkg/apimachinery/errutil"
 )
@@ -95,31 +93,3 @@ func makeUnexpectedNodeTypeError(refID, nodeType string) error {
 
 	return UnexpectedNodeTypeError.Build(data)
 }
-
-var DuplicateStringColumnError = errutil.NewBase(
-	errutil.StatusBadRequest, "sse.duplicateStringColumns").MustTemplate(
-	"your SQL query returned {{ .Public.count }} rows with duplicate values across the string columns, which is not allowed for alerting. Examples: ({{ .Public.examples }}). Hint: use GROUP BY or aggregation (e.g. MAX(), AVG()) to return one row per unique combination.",
-	errutil.WithPublic("SQL query returned duplicate combinations of string column values. Use GROUP BY or aggregation to return one row per combination."),
-)
-
-func makeDuplicateStringColumnError(examples []string) error {
-	const limit = 5
-	sort.Strings(examples)
-	exampleStr := strings.Join(truncateExamples(examples, limit), ", ")
-
-	return DuplicateStringColumnError.Build(errutil.TemplateData{
-		Public: map[string]any{
-			"examples": exampleStr,
-			"count":    len(examples),
-		},
-	})
-}
-
-func truncateExamples(examples []string, limit int) []string {
-	if len(examples) <= limit {
-		return examples
-	}
-	truncated := examples[:limit]
-	truncated = append(truncated, fmt.Sprintf("... and %d more", len(examples)-limit))
-	return truncated
-}