From f9fa9c626dc16b2b31085a58ab97d3fc953ddd96 Mon Sep 17 00:00:00 2001
From: Oliver Tan <otan@cockroachlabs.com>
Date: Wed, 10 Feb 2021 15:04:53 +1100
Subject: [PATCH] sql: use kv_node_status to determine node liveness for
 multiregion

This was a relic before the decision was made -- node liveness was
detected by gossip instead. This changes the code to use SHOW REGIONS
FROM CLUSTER, which aggregates from kv_node_status.

Release note: None
---
 pkg/sql/alter_database.go |  2 +-
 pkg/sql/descriptor.go     |  6 +++---
 pkg/sql/region_util.go    | 24 ++++++++++++++----------
 3 files changed, 18 insertions(+), 14 deletions(-)

diff --git a/pkg/sql/alter_database.go b/pkg/sql/alter_database.go
index 0f163e37b3dc..31861a80768b 100644
--- a/pkg/sql/alter_database.go
+++ b/pkg/sql/alter_database.go
@@ -161,7 +161,7 @@ func (n *alterDatabaseAddRegionNode) startExec(params runParams) error {
 	// Add the region to the database descriptor. This function validates that the region
 	// we're adding is an active member of the cluster and isn't already present in the
 	// RegionConfig.
-	if err := params.p.addRegionToRegionConfig(n.desc, n.n); err != nil {
+	if err := params.p.addRegionToRegionConfig(params.ctx, n.desc, n.n); err != nil {
 		return err
 	}
 
diff --git a/pkg/sql/descriptor.go b/pkg/sql/descriptor.go
index c4e8af9349ce..d3ac262916d5 100644
--- a/pkg/sql/descriptor.go
+++ b/pkg/sql/descriptor.go
@@ -261,9 +261,9 @@ func validateDatabaseRegionConfig(regionConfig descpb.DatabaseDescriptor_RegionC
 // addRegionToRegionConfig adds the supplied region to the RegionConfig in the
 // supplied database descriptor.
 func (p *planner) addRegionToRegionConfig(
-	desc *dbdesc.Mutable, regionToAdd *tree.AlterDatabaseAddRegion,
+	ctx context.Context, desc *dbdesc.Mutable, regionToAdd *tree.AlterDatabaseAddRegion,
 ) error {
-	liveRegions, err := p.getLiveClusterRegions()
+	liveRegions, err := p.getLiveClusterRegions(ctx)
 	if err != nil {
 		return err
 	}
@@ -320,7 +320,7 @@ func (p *planner) createRegionConfig(
 	if err != nil {
 		return nil, err
 	}
-	liveRegions, err := p.getLiveClusterRegions()
+	liveRegions, err := p.getLiveClusterRegions(ctx)
 	if err != nil {
 		return nil, err
 	}
diff --git a/pkg/sql/region_util.go b/pkg/sql/region_util.go
index 9a495b88db51..d9253c2a13d8 100644
--- a/pkg/sql/region_util.go
+++ b/pkg/sql/region_util.go
@@ -52,19 +52,23 @@ func (s *liveClusterRegions) toStrings() []string {
 // getLiveClusterRegions returns a set of live region names in the cluster.
 // A region name is deemed active if there is at least one alive node
 // in the cluster in with locality set to a given region.
-func (p *planner) getLiveClusterRegions() (liveClusterRegions, error) {
-	nodes, err := getAllNodeDescriptors(p)
+func (p *planner) getLiveClusterRegions(ctx context.Context) (liveClusterRegions, error) {
+	rows, err := p.ExtendedEvalContext().ExecCfg.InternalExecutor.QueryEx(
+		ctx,
+		"get_live_cluster_regions",
+		p.txn,
+		sessiondata.InternalExecutorOverride{
+			User: p.SessionData().User(),
+		},
+		"SELECT region FROM [SHOW REGIONS FROM CLUSTER]",
+	)
 	if err != nil {
 		return nil, err
 	}
-	var ret liveClusterRegions = make(map[descpb.RegionName]struct{})
-	for _, node := range nodes {
-		for _, tier := range node.Locality.Tiers {
-			if tier.Key == "region" {
-				ret[descpb.RegionName(tier.Value)] = struct{}{}
-				break
-			}
-		}
+
+	var ret liveClusterRegions = make(map[descpb.RegionName]struct{}, len(rows))
+	for _, row := range rows {
+		ret[descpb.RegionName(*row[0].(*tree.DString))] = struct{}{}
 	}
 	return ret, nil
 }