SQL Expressions: Add sql expression specific timeout and output limit (#104834)

Adds settings for SQL expressions:
 sql_expression_cell_output_limit

Set the maximum number of cells that can be returned from a SQL expression. Default is 100000.

sql_expression_timeout

The duration a SQL expression will run before being cancelled. The default is 10s.

pkg/expr/nodes.go

@@ -20,6 +20,7 @@ import (
 	"github.com/grafana/grafana/pkg/infra/log"
 	"github.com/grafana/grafana/pkg/services/datasources"
 	"github.com/grafana/grafana/pkg/services/featuremgmt"
+	"github.com/grafana/grafana/pkg/setting"
 )
 
 // label that is used when all mathexp.Series have 0 labels to make them identifiable by labels. The value of this label is extracted from value field names
@@ -106,7 +107,7 @@ func (gn *CMDNode) Execute(ctx context.Context, now time.Time, vars mathexp.Vars
 	return gn.Command.Execute(ctx, now, vars, s.tracer, s.metrics)
 }
 
-func buildCMDNode(rn *rawNode, toggles featuremgmt.FeatureToggles, sqlExpressionCellLimit int64) (*CMDNode, error) {
+func buildCMDNode(rn *rawNode, toggles featuremgmt.FeatureToggles, cfg *setting.Cfg) (*CMDNode, error) {
 	commandType, err := GetExpressionCommandType(rn.Query)
 	if err != nil {
 		return nil, fmt.Errorf("invalid command type in expression '%v': %w", rn.RefID, err)
@@ -163,7 +164,7 @@ func buildCMDNode(rn *rawNode, toggles featuremgmt.FeatureToggles, sqlExpression
 	case TypeThreshold:
 		node.Command, err = UnmarshalThresholdCommand(rn)
 	case TypeSQL:
-		node.Command, err = UnmarshalSQLCommand(rn, sqlExpressionCellLimit)
+		node.Command, err = UnmarshalSQLCommand(rn, cfg)
 	default:
 		return nil, fmt.Errorf("expression command type '%v' in expression '%v' not implemented", commandType, rn.RefID)
 	}