sql: split ranges synchronously when creating new tenant

The previous commit taught the split and merge queues about tenant
boundaries, which means that split points will be created asynchronously
when a new tenant is created. However, it is valuable from an isolation
perspective to split off tenant ranges synchronously upon the creation
of a new tenant. This commit adds in such synchronous range splitting to
the `crdb_internal.create_tenant` builtin.

pkg/sql/sqlbase/metadata.go

@@ -197,8 +197,24 @@ func (ms MetadataSchema) GetInitialValues() ([]roachpb.KeyValue, []roachpb.RKey)
 		addDescriptor(sysObj.parentID, sysObj.desc)
 	}
 
-	for _, id := range ms.otherSplitIDs {
-		splits = append(splits, roachpb.RKey(ms.codec.TablePrefix(id)))
+	// The splits slice currently has a split point for each of the object
+	// descriptors in ms.descs. If we're fetching the initial values for the
+	// system tenant, add any additional split point, which correspond to
+	// "pseudo" tables that don't have real descriptors.
+	//
+	// If we're fetching the initial values for a secondary tenant, things are
+	// different. Secondary tenants do not enforce split points at table
+	// boundaries. In fact, if we tried to split at table boundaries, those
+	// splits would quickly be merged away. The only enforced split points are
+	// between secondary tenants (e.g. between /tenant/<id> and /tenant/<id+1>).
+	// So we drop all descriptor split points and replace it with a single split
+	// point at the beginning of this tenant's keyspace.
+	if ms.codec.ForSystemTenant() {
+		for _, id := range ms.otherSplitIDs {
+			splits = append(splits, roachpb.RKey(ms.codec.TablePrefix(id)))
+		}
+	} else {
+		splits = []roachpb.RKey{roachpb.RKey(ms.codec.TenantPrefix())}
 	}
 
 	// Other key/value generation that doesn't fit into databases and

pkg/sql/sqlbase/system.go

@@ -1782,7 +1782,6 @@ func addSystemDatabaseToSchema(
 	defaultSystemZoneConfig *zonepb.ZoneConfig,
 ) {
 	addSystemDescriptorsToSchema(target)
-	// TODO(nvanbenschoten): only do this for the system tenant. Tracked in #48774.
 	addSplitIDs(target)
 	addZoneConfigKVsToSchema(target, defaultZoneConfig, defaultSystemZoneConfig)
 }

pkg/sql/tenant.go

@@ -12,6 +12,7 @@ package sql
 
 import (
 	"context"
+	"time"
 
 	"github.com/cockroachdb/cockroach/pkg/keys"
 	"github.com/cockroachdb/cockroach/pkg/roachpb"
@@ -94,16 +95,27 @@ func (p *planner) CreateTenant(ctx context.Context, tenID uint64, tenInfo []byte
 		return err
 	}
 
-	// TODO(nvanbenschoten): we currently neither split ranges between a single
-	// tenant's tables nor split ranges between different tenant keyspaces. We
-	// should do both. Performing the splits here won't have the desired effect
-	// until we also teach SystemConfig.ComputeSplitKey about tenant tables and
-	// tenant boundaries. Tracked in #48774.
-	_ = splits
+	// Create initial splits for the new tenant. This is performed
+	// non-transactionally, so the range splits will remain even if the
+	// statement's transaction is rolled back. In this case, the manual splits
+	// can and will be merged away after its 1h expiration elapses.
+	//
+	// If the statement's transaction commits and updates the system.tenants
+	// table, the manual splits' expirations will no longer be necessary to
+	// prevent the split points from being merged away. Likewise, if the
+	// transaction did happen to take long enough that the manual splits'
+	// expirations did elapse and the splits were merged away, they would
+	// quickly (but asynchronously) be recreated once the KV layer notices the
+	// updated system.tenants table in the gossipped SystemConfig.
+	expTime := p.ExecCfg().Clock.Now().Add(time.Hour.Nanoseconds(), 0)
+	for _, key := range splits {
+		if err := p.ExecCfg().DB.AdminSplit(ctx, key, expTime); err != nil {
+			return err
+		}
+	}
 
 	// Tenant creation complete! Note that sqlmigrations have not been run yet.
 	// They will be run when a sqlServer bound to this tenant is first launched.
-
 	return nil
 }
 

pkg/sql/tests/testdata/initial_keys

@@ -159,35 +159,8 @@ initial-keys tenant=5
  /Tenant/5/NamespaceTable/30/1/1/29/"ui"/4/1
  /Tenant/5/NamespaceTable/30/1/1/29/"users"/4/1
  /Tenant/5/NamespaceTable/30/1/1/29/"web_sessions"/4/1
-28 splits:
- /Tenant/5/Table/11
- /Tenant/5/Table/12
- /Tenant/5/Table/13
- /Tenant/5/Table/14
- /Tenant/5/Table/15
- /Tenant/5/Table/16
- /Tenant/5/Table/17
- /Tenant/5/Table/18
- /Tenant/5/Table/19
- /Tenant/5/Table/20
- /Tenant/5/Table/21
- /Tenant/5/Table/22
- /Tenant/5/Table/23
- /Tenant/5/Table/24
- /Tenant/5/Table/25
- /Tenant/5/Table/26
- /Tenant/5/Table/27
- /Tenant/5/Table/28
- /Tenant/5/Table/29
- /Tenant/5/NamespaceTable/30
- /Tenant/5/NamespaceTable/Max
- /Tenant/5/Table/32
- /Tenant/5/Table/33
- /Tenant/5/Table/34
- /Tenant/5/Table/35
- /Tenant/5/Table/36
- /Tenant/5/Table/37
- /Tenant/5/Table/38
+1 splits:
+ /Tenant/5
 
 initial-keys tenant=999
 ----
@@ -250,32 +223,5 @@ initial-keys tenant=999
  /Tenant/999/NamespaceTable/30/1/1/29/"ui"/4/1
  /Tenant/999/NamespaceTable/30/1/1/29/"users"/4/1
  /Tenant/999/NamespaceTable/30/1/1/29/"web_sessions"/4/1
-28 splits:
- /Tenant/999/Table/11
- /Tenant/999/Table/12
- /Tenant/999/Table/13
- /Tenant/999/Table/14
- /Tenant/999/Table/15
- /Tenant/999/Table/16
- /Tenant/999/Table/17
- /Tenant/999/Table/18
- /Tenant/999/Table/19
- /Tenant/999/Table/20
- /Tenant/999/Table/21
- /Tenant/999/Table/22
- /Tenant/999/Table/23
- /Tenant/999/Table/24
- /Tenant/999/Table/25
- /Tenant/999/Table/26
- /Tenant/999/Table/27
- /Tenant/999/Table/28
- /Tenant/999/Table/29
- /Tenant/999/NamespaceTable/30
- /Tenant/999/NamespaceTable/Max
- /Tenant/999/Table/32
- /Tenant/999/Table/33
- /Tenant/999/Table/34
- /Tenant/999/Table/35
- /Tenant/999/Table/36
- /Tenant/999/Table/37
- /Tenant/999/Table/38
+1 splits:
+ /Tenant/999