sql: remove two private settings

This commit removes two private settings that could disable planning of
multiple join readers (i.e would disable distribution) and disable
planning merge joiners (i.e. would simply prohibit the use of merge
joiners). It also retires two settings that have been removed after 20.1
was cut.

Release note: None

pkg/settings/registry.go

@@ -62,8 +62,12 @@ var retiredSettings = map[string]struct{}{
 	// removed as of 20.1.
 	"schemachanger.lease.duration":       {},
 	"schemachanger.lease.renew_fraction": {},
-	// removes as of 20.2.
+	// removed as of 20.2.
 	"rocksdb.ingest_backpressure.pending_compaction_threshold": {},
+	"sql.distsql.temp_storage.joins":                           {},
+	"sql.distsql.temp_storage.sorts":                           {},
+	"sql.distsql.distribute_index_joins":                       {},
+	"sql.distsql.merge_joins.enabled":                          {},
 }
 
 // register adds a setting to the registry.

pkg/sql/distsql_physical_planner.go

@@ -24,7 +24,6 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/roachpb"
 	"github.com/cockroachdb/cockroach/pkg/rpc"
 	"github.com/cockroachdb/cockroach/pkg/rpc/nodedialer"
-	"github.com/cockroachdb/cockroach/pkg/settings"
 	"github.com/cockroachdb/cockroach/pkg/settings/cluster"
 	"github.com/cockroachdb/cockroach/pkg/sql/distsql"
 	"github.com/cockroachdb/cockroach/pkg/sql/execinfra"
@@ -110,22 +109,6 @@ var ReplicaOraclePolicy = replicaoracle.BinPackingChoice
 // debugging).
 var logPlanDiagram = envutil.EnvOrDefaultBool("COCKROACH_DISTSQL_LOG_PLAN", false)
 
-// If true, for index joins we instantiate a join reader on every node that
-// has a stream (usually from a table reader). If false, there is a single join
-// reader.
-var distributeIndexJoin = settings.RegisterBoolSetting(
-	"sql.distsql.distribute_index_joins",
-	"if set, for index joins we instantiate a join reader on every node that has a "+
-		"stream; if not set, we use a single join reader",
-	true,
-)
-
-var planMergeJoins = settings.RegisterBoolSetting(
-	"sql.distsql.merge_joins.enabled",
-	"if set, we plan merge joins when possible",
-	true,
-)
-
 // NewDistSQLPlanner initializes a DistSQLPlanner.
 //
 // nodeDesc is the descriptor of the node on which this planner runs. It is used
@@ -1861,7 +1844,7 @@ func (dsp *DistSQLPlanner) createPlanForIndexJoin(
 	if err != nil {
 		return PhysicalPlan{}, err
 	}
-	if distributeIndexJoin.Get(&dsp.st.SV) && len(plan.ResultRouters) > 1 {
+	if len(plan.ResultRouters) > 1 {
 		// Instantiate one join reader for every stream.
 		plan.AddNoGroupingStage(
 			execinfrapb.ProcessorCoreUnion{JoinReader: &joinReaderSpec},
@@ -1870,14 +1853,9 @@ func (dsp *DistSQLPlanner) createPlanForIndexJoin(
 			dsp.convertOrdering(n.reqOrdering, plan.PlanToStreamColMap),
 		)
 	} else {
-		// Use a single join reader (if there is a single stream, on that node; if
-		// not, on the gateway node).
-		node := dsp.nodeDesc.NodeID
-		if len(plan.ResultRouters) == 1 {
-			node = plan.Processors[plan.ResultRouters[0]].Node
-		}
+		// We have a single stream, so use a single join reader on that node.
 		plan.AddSingleGroupStage(
-			node,
+			plan.Processors[plan.ResultRouters[0]].Node,
 			execinfrapb.ProcessorCoreUnion{JoinReader: &joinReaderSpec},
 			post,
 			types,
@@ -2212,7 +2190,7 @@ func (dsp *DistSQLPlanner) createPlanForJoin(
 	if numEq := len(n.pred.leftEqualityIndices); numEq != 0 {
 		nodes = findJoinProcessorNodes(leftRouters, rightRouters, p.Processors)
 
-		if planMergeJoins.Get(&dsp.st.SV) && len(n.mergeJoinOrdering) > 0 {
+		if len(n.mergeJoinOrdering) > 0 {
 			// TODO(radu): we currently only use merge joins when we have an ordering on
 			// all equality columns. We should relax this by either:
 			//  - implementing a hybrid hash/merge processor which implements merge
@@ -3025,7 +3003,7 @@ func (dsp *DistSQLPlanner) createPlanForSetOp(
 		//    group uses a hashmap on the remaining columns
 		//  - or: adding a sort processor to complete the order
 		var core execinfrapb.ProcessorCoreUnion
-		if !planMergeJoins.Get(&dsp.st.SV) || len(mergeOrdering.Columns) < len(streamCols) {
+		if len(mergeOrdering.Columns) < len(streamCols) {
 			core.HashJoiner = &execinfrapb.HashJoinerSpec{
 				LeftEqColumns:  eqCols,
 				RightEqColumns: eqCols,