server: fix DataDistribution server error when creating a tenant

This is a stop-gap commit that enables the DataDistribution endpoint
to handle the parts of the key space belonging to secondary tenants
without error.

Despite no error, the result returned for secondary tenants is not correct.
The DataDistribution endpoint was written before cockroachdb#79700, and therefore
doesn't know that multiple tables can exist within a range.

Additionally, the results for the system tenant will be incorrect soon
because cockroachdb#81008 is in progress.

Fixes: cockroachdb#97993
Release note: None

pkg/ccl/serverccl/admin_test.go

@@ -47,13 +47,14 @@ func TestAdminAPIDataDistributionPartitioning(t *testing.T) {
 	defer leaktest.AfterTest(t)()
 	defer log.Scope(t).Close(t)
 
+	// Need to disable the test tenant because this test fails
+	// when run through a tenant (with internal server error).
+	// More investigation is required. Tracked with #76387.
+	disableDefaultTestTenant := true
 	testCluster := serverutils.StartNewTestCluster(t, 3,
 		base.TestClusterArgs{
 			ServerArgs: base.TestServerArgs{
-				// Need to disable the test tenant because this test fails
-				// when run through a tenant (with internal server error).
-				// More investigation is required. Tracked with #76387.
-				DisableDefaultTestTenant: true,
+				DisableDefaultTestTenant: disableDefaultTestTenant,
 			},
 		})
 	defer testCluster.Stopper().Stop(context.Background())
@@ -81,6 +82,11 @@ func TestAdminAPIDataDistributionPartitioning(t *testing.T) {
 	sqlDB.Exec(t, `ALTER PARTITION us OF TABLE comments CONFIGURE ZONE USING gc.ttlseconds = 9001`)
 	sqlDB.Exec(t, `ALTER PARTITION eu OF TABLE comments CONFIGURE ZONE USING gc.ttlseconds = 9002`)
 
+	if disableDefaultTestTenant {
+		// Make sure secondary tenants don't cause the endpoint to error.
+		sqlDB.Exec(t, "CREATE TENANT 'app'")
+	}
+
 	// Assert that we get all roachblog zone configs back.
 	expectedZoneConfigNames := map[string]struct{}{
 		"PARTITION eu OF INDEX roachblog.public.comments@comments_pkey": {},

pkg/server/admin.go

@@ -3082,6 +3082,17 @@ func (s *adminServer) dataDistributionHelper(
 			if err != nil {
 				return err
 			}
+
+			// A range descriptor for a secondary tenant may not contain
+			// a table prefix. Often, the start key for a tenant will be just
+			// the tenant prefix itself, e.g. `/Tenant/2`. Once the tenant prefix
+			// is stripped inside `DecodeTablePrefix`, nothing (aka `/Min`) is left.
+			keySansPrefix, _ := keys.MakeSQLCodec(tenID).StripTenantPrefix(rangeDesc.StartKey.AsRawKey())
+			if keys.MinKey.Equal(keySansPrefix) {
+				// There's no table prefix to be decoded.
+				// Try the next descriptor.
+				continue
+			}
 			_, tableID, err := keys.MakeSQLCodec(tenID).DecodeTablePrefix(rangeDesc.StartKey.AsRawKey())
 			if err != nil {
 				return err

pkg/server/admin_test.go

@@ -2220,6 +2220,9 @@ func TestAdminAPIDataDistribution(t *testing.T) {
 	sqlDB.Exec(t, `CREATE DATABASE "sp'ec\ch""ars"`)
 	sqlDB.Exec(t, `CREATE TABLE "sp'ec\ch""ars"."more\spec'chars" (id INT PRIMARY KEY)`)
 
+	// Make sure secondary tenants don't cause the endpoint to error.
+	sqlDB.Exec(t, "CREATE TENANT 'app'")
+
 	// Verify that we see their replicas in the DataDistribution response, evenly spread
 	// across the test cluster's three nodes.