Merge pull request #18458 from spongedu/support_exists_database

support EXISTS DATABASE syntax

src/Interpreters/InterpreterExistsQuery.cpp

@@ -53,6 +53,12 @@ BlockInputStreamPtr InterpreterExistsQuery::executeImpl()
             result = DatabaseCatalog::instance().isTableExist({database, exists_query->table}, context);
         }
     }
+    else if ((exists_query = query_ptr->as<ASTExistsDatabaseQuery>()))
+    {
+        String database = context.resolveDatabase(exists_query->database);
+        context.checkAccess(AccessType::SHOW_DATABASES, database);
+        result = DatabaseCatalog::instance().isDatabaseExist(database);
+    }
     else if ((exists_query = query_ptr->as<ASTExistsDictionaryQuery>()))
     {
         if (exists_query->temporary)

src/Interpreters/InterpreterFactory.cpp

@@ -148,6 +148,10 @@ std::unique_ptr<IInterpreter> InterpreterFactory::get(ASTPtr & query, Context &
     {
         return std::make_unique<InterpreterOptimizeQuery>(query, context);
     }
+    else if (query->as<ASTExistsDatabaseQuery>())
+    {
+        return std::make_unique<InterpreterExistsQuery>(query, context);
+    }
     else if (query->as<ASTExistsTableQuery>())
     {
         return std::make_unique<InterpreterExistsQuery>(query, context);

src/Parsers/ParserTablePropertiesQuery.cpp

@@ -34,15 +34,23 @@ bool ParserTablePropertiesQuery::parseImpl(Pos & pos, ASTPtr & node, Expected &
     bool temporary = false;
     if (s_exists.ignore(pos, expected))
     {
-        if (s_temporary.ignore(pos, expected))
-            temporary = true;
-
-        if (s_table.checkWithoutMoving(pos, expected))
-            query = std::make_shared<ASTExistsTableQuery>();
-        else if (s_dictionary.checkWithoutMoving(pos, expected))
-            query = std::make_shared<ASTExistsDictionaryQuery>();
+        if (s_database.ignore(pos, expected))
+        {
+            query = std::make_shared<ASTExistsDatabaseQuery>();
+            parse_only_database_name = true;
+        }
         else
-            query = std::make_shared<ASTExistsTableQuery>();
+        {
+            if (s_temporary.ignore(pos, expected))
+                temporary = true;
+
+            if (s_table.checkWithoutMoving(pos, expected))
+                query = std::make_shared<ASTExistsTableQuery>();
+            else if (s_dictionary.checkWithoutMoving(pos, expected))
+                query = std::make_shared<ASTExistsDictionaryQuery>();
+            else
+                query = std::make_shared<ASTExistsTableQuery>();
+        }
     }
     else if (s_show.ignore(pos, expected))
     {

src/Parsers/TablePropertiesQueriesASTs.h

@@ -7,6 +7,14 @@
 namespace DB
 {
 
+struct ASTExistsDatabaseQueryIDAndQueryNames
+{
+    static constexpr auto ID = "ExistsDatabaseQuery";
+    static constexpr auto Query = "EXISTS DATABASE";
+    /// No temporary databases are supported, just for parsing
+    static constexpr auto QueryTemporary = "";
+};
+
 struct ASTExistsTableQueryIDAndQueryNames
 {
     static constexpr auto ID = "ExistsTableQuery";
@@ -51,6 +59,7 @@ struct ASTDescribeQueryExistsQueryIDAndQueryNames
     static constexpr auto QueryTemporary = "DESCRIBE TEMPORARY TABLE";
 };
 
+using ASTExistsDatabaseQuery = ASTQueryWithTableAndOutputImpl<ASTExistsDatabaseQueryIDAndQueryNames>;
 using ASTExistsTableQuery = ASTQueryWithTableAndOutputImpl<ASTExistsTableQueryIDAndQueryNames>;
 using ASTExistsDictionaryQuery = ASTQueryWithTableAndOutputImpl<ASTExistsDictionaryQueryIDAndQueryNames>;
 using ASTShowCreateTableQuery = ASTQueryWithTableAndOutputImpl<ASTShowCreateTableQueryIDAndQueryNames>;

tests/queries/0_stateless/01048_exists_query.reference

@@ -2,6 +2,8 @@
 0
 0
 0
+1
+0
 0
 0
 1

tests/queries/0_stateless/01048_exists_query.sql

@@ -3,7 +3,9 @@ EXISTS TABLE db_01048.t_01048;
 EXISTS DICTIONARY db_01048.t_01048;
 
 DROP DATABASE IF EXISTS db_01048;
+EXISTS DATABASE db_01048;
 CREATE DATABASE db_01048;
+EXISTS DATABASE db_01048;
 
 DROP TABLE IF EXISTS db_01048.t_01048;
 EXISTS db_01048.t_01048;