SQL Expressions: Add endpoint to get Schemas (#108864)

Return the SQL schema for all DS queries in request (to provide information to AI / Autocomplete for SQL expressions).

All DS queries are treated as if they were inputs to SQL expressions in terms of conversion, regardless if they are selected in a query or not.

Requires feature toggle queryService = true

Endpoint is apis/query.grafana.app/v0alpha1/namespaces/default/sqlschemas

---------

Co-authored-by: Todd Treece <360020+toddtreece@users.noreply.github.com>

pkg/services/query/expr_sql_schema.go

@@ -0,0 +1,75 @@
+package query
+
+import (
+	"context"
+
+	"github.com/grafana/grafana/pkg/api/dtos"
+	"github.com/grafana/grafana/pkg/apimachinery/errutil"
+	"github.com/grafana/grafana/pkg/apimachinery/identity"
+	"github.com/grafana/grafana/pkg/expr"
+	"github.com/grafana/grafana/pkg/infra/log"
+	"github.com/grafana/grafana/pkg/services/datasources"
+	"github.com/grafana/grafana/pkg/services/dsquerierclient"
+	"github.com/grafana/grafana/pkg/services/validations"
+)
+
+func (s *ServiceImpl) GetSQLSchemas(ctx context.Context, user identity.Requester, reqDTO dtos.MetricRequest) (expr.SQLSchemas, error) {
+	//TODO DEdupe code
+
+	parsedReq, err := s.parseMetricRequest(ctx, user, false, reqDTO, false)
+	if err != nil {
+		return expr.SQLSchemas{}, err
+	}
+	exprReq := expr.Request{
+		Queries: []expr.Query{},
+	}
+
+	if user != nil { // for passthrough authentication, SSE does not authenticate
+		exprReq.User = user
+		exprReq.OrgId = user.GetOrgID()
+	}
+
+	for _, pq := range parsedReq.getFlattenedQueries() {
+		if pq.datasource == nil {
+			return nil, ErrMissingDataSourceInfo.Build(errutil.TemplateData{
+				Public: map[string]any{
+					"RefId": pq.query.RefID,
+				},
+			})
+		}
+
+		exprReq.Queries = append(exprReq.Queries, expr.Query{
+			JSON:          pq.query.JSON,
+			Interval:      pq.query.Interval,
+			RefID:         pq.query.RefID,
+			MaxDataPoints: pq.query.MaxDataPoints,
+			QueryType:     pq.query.QueryType,
+			DataSource:    pq.datasource,
+			TimeRange: expr.AbsoluteTimeRange{
+				From: pq.query.TimeRange.From,
+				To:   pq.query.TimeRange.To,
+			},
+		})
+	}
+
+	return s.expressionService.GetSQLSchemas(ctx, exprReq)
+}
+
+func GetSQLSchemas(ctx context.Context, log log.Logger, dscache datasources.CacheService, exprService *expr.Service, reqDTO dtos.MetricRequest, qsDatasourceClientBuilder dsquerierclient.QSDatasourceClientBuilder, headers map[string]string) (expr.SQLSchemas, error) {
+	s := &ServiceImpl{
+		log:                        log,
+		dataSourceCache:            dscache,
+		expressionService:          exprService,
+		dataSourceRequestValidator: validations.ProvideValidator(),
+		qsDatasourceClientBuilder:  qsDatasourceClientBuilder,
+		headers:                    headers,
+		concurrentQueryLimit:       16, // TODO: make it configurable
+	}
+
+	user, err := identity.GetRequester(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	return s.GetSQLSchemas(ctx, user, reqDTO)
+}

pkg/services/query/query.go

@@ -73,6 +73,8 @@ type Service interface {
 
 	// this is more "forward compatible", for example supports per-query time ranges
 	QueryDataNew(ctx context.Context, user identity.Requester, skipDSCache bool, reqDTO dtos.MetricRequest) (*backend.QueryDataResponse, error)
+
+	GetSQLSchemas(ctx context.Context, user identity.Requester, reqDTO dtos.MetricRequest) (expr.SQLSchemas, error)
 }
 
 // Gives us compile time error if the service does not adhere to the contract of the interface

pkg/services/query/query_service_mock.go

@@ -4,10 +4,12 @@ package query
 
 import (
 	context "context"
+	"fmt"
 
 	backend "github.com/grafana/grafana-plugin-sdk-go/backend"
 
 	dtos "github.com/grafana/grafana/pkg/api/dtos"
+	"github.com/grafana/grafana/pkg/expr"
 
 	identity "github.com/grafana/grafana/pkg/apimachinery/identity"
 
@@ -97,6 +99,10 @@ func (_m *FakeQueryService) Run(ctx context.Context) error {
 	return r0
 }
 
+func (_m *FakeQueryService) GetSQLSchemas(ctx context.Context, user identity.Requester, reqDTO dtos.MetricRequest) (expr.SQLSchemas, error) {
+	return nil, fmt.Errorf("sql schema endpoint not supported with public dashboards")
+}
+
 // NewFakeQueryService creates a new instance of FakeQueryService. It also registers a testing interface on the mock and a cleanup function to assert the mocks expectations.
 // The first argument is typically a *testing.T value.
 func NewFakeQueryService(t interface {