[pg15-upgrade] test: convert backslash d and comment tests to c++ uni…

…t tests

Summary:
Adding `Pg15UpgradeTestBase` class to upgrade from 2.20.2.4 to latest (pg15) and helper functions to keep the cluster in a mixed mode.
Adding a test to check the pg versions at various stages, and one that creates a table with 3 tablets, and 100 row and ensures the row count is correct when queried in mixed mode.
Converted `test_upgrade_backslash_d.sh`, and `test_upgrade_comment.sh` to c++ unit tests.

Fixes to UpgradeTestBase:
- Enabling `ysql_enable_db_catalog_version_mode` and running necessary commands to set up per db catalog mode.
- Disabling `ysql_yb_enable_expression_pushdown`
- Fixed `UpgradeTestBase::RollbackVolatileAutoFlags` to run `RollbackYsqlMajorVersion` AFTER `RestartAllTServersInOldVersion`

Test Plan:
Pg15UpgradeTest.CheckVersion
Pg15UpgradeTest.UpgradeWithOneTable
Pg15UpgradeTest.BackslashD
Pg15UpgradeTest.Comments

Reviewers: tfoucher, telgersma, jason, fizaa

Reviewed By: tfoucher

Subscribers: ybase

Differential Revision: https://phorge.dev.yugabyte.com/D38487

src/yb/integration-tests/CMakeLists.txt

@@ -96,6 +96,7 @@ set(INTEGRATION_TESTS_SRCS
   xcluster/xcluster_ysql_test_base.cc
   xcluster/xcluster_ycql_test_base.cc
   xcluster/xcluster_ddl_replication_test_base.cc
+  upgrade-tests/pg15_upgrade_test_base.cc
   upgrade-tests/upgrade_test_base.cc
 )
 
@@ -260,6 +261,7 @@ ADD_YB_TEST(xcluster/xcluster-test)
 ADD_YB_TEST(xcluster/xcluster_outbound_replication_group-itest)
 ADD_YB_TEST(retryable_request-test)
 ADD_YB_TEST(upgrade-tests/basic_upgrade-test)
+ADD_YB_TEST(upgrade-tests/pg15_upgrade-test)
 
 set(YB_TEST_LINK_LIBS_SAVED ${YB_TEST_LINK_LIBS})
 set(YB_TEST_LINK_LIBS ${YB_TEST_LINK_LIBS} cassandra)

src/yb/integration-tests/external_mini_cluster.cc

@@ -1995,6 +1995,15 @@ void ExternalMiniCluster::RemoveExtraFlagOnTServers(const std::string& flag) {
   }
 }
 
+Status ExternalMiniCluster::AddAndSetExtraFlag(const std::string& flag, const std::string& value) {
+  for (const auto& daemon : daemons()) {
+    daemon->AddExtraFlag(flag, value);
+    RETURN_NOT_OK_PREPEND(
+        SetFlag(daemon, flag, value), Format("Failed to set flag on $0", daemon->id()));
+  }
+
+  return Status::OK();
+}
 
 uint16_t ExternalMiniCluster::AllocateFreePort() {
   // This will take a file lock ensuring the port does not get claimed by another thread/process

src/yb/integration-tests/external_mini_cluster.h

@@ -504,6 +504,10 @@ class ExternalMiniCluster : public MiniClusterBase {
   // to get any effect of that change.
   void RemoveExtraFlagOnTServers(const std::string& flag);
 
+  // Adds the given flag to the extra flags on all servers. Also dynamically sets the flag on the
+  // running processes. Non runtime flags would still require a restart.
+  Status AddAndSetExtraFlag(const std::string& flag, const std::string& value);
+
   // Allocates a free port and stores a file lock guarding access to that port into an internal
   // array of file locks.
   uint16_t AllocateFreePort();

src/yb/integration-tests/upgrade-tests/pg15_upgrade-test.cc

@@ -0,0 +1,171 @@
+// Copyright (c) YugabyteDB, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
+// in compliance with the License.  You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software distributed under the License
+// is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
+// or implied.  See the License for the specific language governing permissions and limitations
+// under the License.
+//
+
+#include "yb/integration-tests/upgrade-tests/pg15_upgrade_test_base.h"
+
+#include "yb/yql/pgwrapper/libpq_utils.h"
+
+namespace yb {
+
+class Pg15UpgradeTest : public Pg15UpgradeTestBase {
+ public:
+  Pg15UpgradeTest() = default;
+};
+
+TEST_F(Pg15UpgradeTest, CheckVersion) {
+  const auto kSelectVersion = "SELECT version()";
+  {
+    auto conn = ASSERT_RESULT(cluster_->ConnectToDB());
+    auto version = ASSERT_RESULT(conn.FetchRowAsString(kSelectVersion));
+    ASSERT_STR_CONTAINS(version, old_version_info().version);
+  }
+
+  ASSERT_OK(UpgradeClusterToMixedMode());
+
+  {
+    auto conn = ASSERT_RESULT(CreateConnToTs(kMixedModeTserverPg15));
+    auto version = ASSERT_RESULT(conn.FetchRowAsString(kSelectVersion));
+    ASSERT_STR_CONTAINS(version, current_version_info().version_number());
+  }
+  {
+    auto conn = ASSERT_RESULT(CreateConnToTs(kMixedModeTserverPg11));
+    auto version = ASSERT_RESULT(conn.FetchRowAsString(kSelectVersion));
+    ASSERT_STR_CONTAINS(version, old_version_info().version);
+  }
+
+  ASSERT_OK(FinalizeUpgradeFromMixedMode());
+
+  {
+    auto conn = ASSERT_RESULT(cluster_->ConnectToDB());
+    auto version = ASSERT_RESULT(conn.FetchRowAsString(kSelectVersion));
+    ASSERT_STR_CONTAINS(version, current_version_info().version_number());
+  }
+}
+
+TEST_F(Pg15UpgradeTest, SimpleTable) {
+  const size_t kRowCount = 100;
+  // Create a table with 3 tablets and kRowCount rows so that each tablet has at least a few rows.
+  ASSERT_OK(ExecuteStatements(
+      {"CREATE TABLE t (a INT) SPLIT INTO 3 TABLETS",
+       Format("INSERT INTO t VALUES(generate_series(1, $0))", kRowCount)}));
+  static const auto kSelectFromTable = "SELECT * FROM t";
+
+  ASSERT_OK(UpgradeClusterToMixedMode());
+
+  {
+    auto conn = ASSERT_RESULT(CreateConnToTs(kMixedModeTserverPg15));
+    auto count = ASSERT_RESULT(conn.Fetch(kSelectFromTable));
+    ASSERT_EQ(PQntuples(count.get()), kRowCount);
+  }
+  {
+    auto conn = ASSERT_RESULT(CreateConnToTs(kMixedModeTserverPg11));
+    auto count = ASSERT_RESULT(conn.Fetch(kSelectFromTable));
+    ASSERT_EQ(PQntuples(count.get()), kRowCount);
+  }
+
+  ASSERT_OK(FinalizeUpgradeFromMixedMode());
+
+  // Verify row count from a random tserver.
+  {
+    auto conn = ASSERT_RESULT(cluster_->ConnectToDB());
+    auto count = ASSERT_RESULT(conn.Fetch(kSelectFromTable));
+    ASSERT_EQ(PQntuples(count.get()), kRowCount);
+  }
+}
+
+TEST_F(Pg15UpgradeTest, BackslashD) {
+  ASSERT_OK(ExecuteStatement("CREATE TABLE t (a INT)"));
+  static const auto kBackslashD = "\\d";
+  static const auto kExpectedResult =
+      "        List of relations\n"
+      " Schema | Name | Type  |  Owner   \n"
+      "--------+------+-------+----------\n"
+      " public | t    | table | postgres\n"
+      "(1 row)\n\n";
+
+  auto result = ASSERT_RESULT(ExecuteViaYsqlsh(kBackslashD));
+  ASSERT_EQ(result, kExpectedResult);
+
+  ASSERT_OK(UpgradeClusterToMixedMode());
+
+  result = ASSERT_RESULT(ExecuteViaYsqlshOnTs(kBackslashD, kMixedModeTserverPg15));
+  ASSERT_EQ(result, kExpectedResult);
+  result = ASSERT_RESULT(ExecuteViaYsqlshOnTs(kBackslashD, kMixedModeTserverPg11));
+  ASSERT_EQ(result, kExpectedResult);
+
+  ASSERT_OK(FinalizeUpgradeFromMixedMode());
+
+  // Verify the result from a random tserver.
+  result = ASSERT_RESULT(ExecuteViaYsqlsh(kBackslashD));
+  ASSERT_EQ(result, kExpectedResult);
+}
+
+TEST_F(Pg15UpgradeTest, Comments) {
+  const auto kPg11DatabaseComment = "PG11: [db] I came first!";
+  const auto kPg11TableComment = "PG11: [table] I came first!";
+  ASSERT_OK(ExecuteStatements(
+      {"CREATE TABLE t (a int)",
+       Format("COMMENT ON DATABASE yugabyte IS '$0'", kPg11DatabaseComment),
+       Format("COMMENT ON TABLE t IS '$0'", kPg11TableComment)}));
+
+  ASSERT_OK(UpgradeClusterToMixedMode());
+
+  const auto kSelectDatabaseComment =
+      "SELECT pg_catalog.shobj_description(d.oid, 'pg_database') FROM pg_catalog.pg_database d "
+      "WHERE datname = 'yugabyte'";
+  const auto kSelectTableComment =
+      "SELECT description from pg_description JOIN pg_class on pg_description.objoid = "
+      "pg_class.oid WHERE relname = 't'";
+
+  auto check_pg11_comment = [&](pgwrapper::PGConn& conn) {
+    auto comment = ASSERT_RESULT(conn.FetchRow<std::string>(kSelectDatabaseComment));
+    ASSERT_EQ(comment, kPg11DatabaseComment);
+    comment = ASSERT_RESULT(conn.FetchRow<std::string>(kSelectTableComment));
+    ASSERT_EQ(comment, kPg11TableComment);
+  };
+
+  {
+    auto conn = ASSERT_RESULT(CreateConnToTs(kMixedModeTserverPg15));
+    ASSERT_NO_FATALS(check_pg11_comment(conn));
+  }
+  {
+    auto conn = ASSERT_RESULT(CreateConnToTs(kMixedModeTserverPg11));
+    ASSERT_NO_FATALS(check_pg11_comment(conn));
+  }
+
+  ASSERT_OK(FinalizeUpgradeFromMixedMode());
+
+  // Check the comment from a random tserver.
+  {
+    auto conn = ASSERT_RESULT(cluster_->ConnectToDB());
+    ASSERT_NO_FATALS(check_pg11_comment(conn));
+  }
+
+  // Update the comment.
+  const auto kPg15DatabaseComment = "PG15: [db] I am better than you!";
+  const auto kPg15TableComment = "PG15: [table] I am better than you!";
+  ASSERT_OK(ExecuteStatements(
+      {Format("COMMENT ON DATABASE yugabyte IS '$0'", kPg15DatabaseComment),
+       Format("COMMENT ON TABLE t IS '$0'", kPg15TableComment)}));
+
+  // Check the new comment from a random tserver.
+  {
+    auto conn = ASSERT_RESULT(cluster_->ConnectToDB());
+    auto comment = ASSERT_RESULT(conn.FetchRow<std::string>(kSelectDatabaseComment));
+    ASSERT_EQ(comment, kPg15DatabaseComment);
+    comment = ASSERT_RESULT(conn.FetchRow<std::string>(kSelectTableComment));
+    ASSERT_EQ(comment, kPg15TableComment);
+  }
+}
+
+}  // namespace yb