Add SHOW WARNINGS support in MySQL interface

ClickHouse · Jan 17, 2024 · cb8372a · cb8372a
1 parent 7731297
commit cb8372a
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Showing 3 changed files with 41 additions and 0 deletions.
diff --git a/src/Server/MySQLHandler.cpp b/src/Server/MySQLHandler.cpp
@@ -61,6 +61,8 @@ namespace ErrorCodes
 static const size_t PACKET_HEADER_SIZE = 4;
 static const size_t SSL_REQUEST_PAYLOAD_SIZE = 32;
 
+static String showWarningsReplacementQuery(const String & query);
+static String showCountWarningsReplacementQuery(const String & query);
 static String selectEmptyReplacementQuery(const String & query);
 static String showTableStatusReplacementQuery(const String & query);
 static String killConnectionIdReplacementQuery(const String & query);
@@ -86,6 +88,8 @@ MySQLHandler::MySQLHandler(
     if (ssl_enabled)
         server_capabilities |= CLIENT_SSL;
 
+    replacements.emplace("SHOW WARNINGS", showWarningsReplacementQuery);
+    replacements.emplace("SHOW COUNT(*) WARNINGS", showCountWarningsReplacementQuery);
     replacements.emplace("KILL QUERY", killConnectionIdReplacementQuery);
     replacements.emplace("SHOW TABLE STATUS LIKE", showTableStatusReplacementQuery);
     replacements.emplace("SHOW VARIABLES", selectEmptyReplacementQuery);
@@ -544,6 +548,18 @@ static bool isFederatedServerSetupSetCommand(const String & query)
     return re2::RE2::FullMatch(query, expr);
 }
 
+/// Always return an empty set with appropriate column definitions for SHOW WARNINGS queries
+/// See also: https://dev.mysql.com/doc/refman/8.0/en/show-warnings.html
+static String showWarningsReplacementQuery([[maybe_unused]] const String & query)
+{
+    return "SELECT '' AS Level, 0::UInt32 AS Code, '' AS Message WHERE false";
+}
+
+static String showCountWarningsReplacementQuery([[maybe_unused]] const String & query)
+{
+    return "SELECT 0::UInt64 AS `@@session.warning_count`";
+}
+
 /// Replace "[query(such as SHOW VARIABLES...)]" into "".
 static String selectEmptyReplacementQuery(const String & query)
 {

diff --git a/tests/queries/0_stateless/02968_mysql_show_warnings.reference b/tests/queries/0_stateless/02968_mysql_show_warnings.reference
@@ -0,0 +1,6 @@
+@@session.warning_count
+0
+@@session.warning_count
+0
+@@warning_count
+0
diff --git a/tests/queries/0_stateless/02968_mysql_show_warnings.sh b/tests/queries/0_stateless/02968_mysql_show_warnings.sh
@@ -0,0 +1,19 @@
+#!/usr/bin/env bash
+# Tags: no-fasttest
+# Tag no-fasttest: requires mysql client
+
+# Tests the override of certain MySQL proprietary settings to ClickHouse native settings
+
+CURDIR=$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)
+# shellcheck source=../shell_config.sh
+. "$CURDIR"/../shell_config.sh
+
+${MYSQL_CLIENT} --execute "SHOW WARNINGS;"
+${MYSQL_CLIENT} --execute "show warnings;"
+${MYSQL_CLIENT} --execute "SHOW WARNINGS LIMIT 100;"
+${MYSQL_CLIENT} --execute "show warnings limit 100;"
+${MYSQL_CLIENT} --execute "SHOW WARNINGS LIMIT 100 OFFSET 100;"
+${MYSQL_CLIENT} --execute "show warnings limit 100 offset 100;"
+${MYSQL_CLIENT} --execute "SHOW COUNT(*) WARNINGS;"
+${MYSQL_CLIENT} --execute "show count(*) warnings;"
+${MYSQL_CLIENT} --execute "SELECT @@session.warning_count;"