diff --git a/dbms/src/Compression/CompressionFactory.h b/dbms/src/Compression/CompressionFactory.h
index db28a19201154f0e3ee2f848bdde87db45fef125..b36bed1cf8eb07228ef4499bbb57dc200e1ce18a 100644
--- a/dbms/src/Compression/CompressionFactory.h
+++ b/dbms/src/Compression/CompressionFactory.h
@@ -1,14 +1,17 @@
 #pragma once
 
-#include <memory>
+#include <Compression/CompressionInfo.h>
+#include <Compression/ICompressionCodec.h>
+#include <DataTypes/IDataType.h>
+#include <Parsers/IAST_fwd.h>
+#include <Common/IFactoryWithAliases.h>
+
+#include <ext/singleton.h>
+
 #include <functional>
+#include <memory>
 #include <optional>
 #include <unordered_map>
-#include <ext/singleton.h>
-#include <DataTypes/IDataType.h>
-#include <Common/IFactoryWithAliases.h>
-#include <Compression/ICompressionCodec.h>
-#include <Compression/CompressionInfo.h>
 
 namespace DB
 {
@@ -19,10 +22,6 @@ using CompressionCodecPtr = std::shared_ptr<ICompressionCodec>;
 
 using CodecNameWithLevel = std::pair<String, std::optional<int>>;
 
-class IAST;
-
-using ASTPtr = std::shared_ptr<IAST>;
-
 /** Creates a codec object by name of compression algorithm family and parameters.
  */
 class CompressionCodecFactory final : public ext::singleton<CompressionCodecFactory>
diff --git a/dbms/src/DataTypes/DataTypeFactory.h b/dbms/src/DataTypes/DataTypeFactory.h
index 95cda9002f4e221d66d07b6906a8a86a29c70a44..c6ef100bbb79ece7d5a0a94a40bc97cb557d3bec 100644
--- a/dbms/src/DataTypes/DataTypeFactory.h
+++ b/dbms/src/DataTypes/DataTypeFactory.h
@@ -1,12 +1,15 @@
 #pragma once
 
-#include <memory>
-#include <functional>
-#include <unordered_map>
-#include <Common/IFactoryWithAliases.h>
 #include <DataTypes/IDataType.h>
+#include <Parsers/IAST_fwd.h>
+#include <Common/IFactoryWithAliases.h>
+
 #include <ext/singleton.h>
 
+#include <functional>
+#include <memory>
+#include <unordered_map>
+
 
 namespace DB
 {
@@ -17,9 +20,6 @@ using DataTypePtr = std::shared_ptr<const IDataType>;
 class IDataTypeDomain;
 using DataTypeDomainPtr = std::unique_ptr<const IDataTypeDomain>;
 
-class IAST;
-using ASTPtr = std::shared_ptr<IAST>;
-
 
 /** Creates a data type by name of data type family and parameters.
   */
diff --git a/dbms/src/Databases/IDatabase.h b/dbms/src/Databases/IDatabase.h
index e6b67a87c9b8faffc2c746aac2ec12c99c814f29..7c0d501fc60e6019c0971176ac198ec263f71eec 100644
--- a/dbms/src/Databases/IDatabase.h
+++ b/dbms/src/Databases/IDatabase.h
@@ -1,16 +1,18 @@
 #pragma once
 
-#include <Core/Types.h>
 #include <Core/NamesAndTypes.h>
+#include <Core/Types.h>
+#include <Interpreters/Context.h>
+#include <Parsers/IAST_fwd.h>
 #include <Storages/ColumnsDescription.h>
 #include <Storages/IndicesDescription.h>
-#include <ctime>
-#include <memory>
-#include <functional>
 #include <Poco/File.h>
-#include <Common/escapeForFileName.h>
 #include <Common/ThreadPool.h>
-#include <Interpreters/Context.h>
+#include <Common/escapeForFileName.h>
+
+#include <ctime>
+#include <functional>
+#include <memory>
 
 
 namespace DB
@@ -21,9 +23,6 @@ class Context;
 class IStorage;
 using StoragePtr = std::shared_ptr<IStorage>;
 
-class IAST;
-using ASTPtr = std::shared_ptr<IAST>;
-
 struct Settings;
 
 
@@ -157,4 +156,3 @@ using DatabasePtr = std::shared_ptr<IDatabase>;
 using Databases = std::map<String, DatabasePtr>;
 
 }
-
diff --git a/dbms/src/Interpreters/Aliases.h b/dbms/src/Interpreters/Aliases.h
index 80976c7551f10c7d79950460f2669e82cd757273..521594422243e60bb602b9552e7922c4147a7735 100644
--- a/dbms/src/Interpreters/Aliases.h
+++ b/dbms/src/Interpreters/Aliases.h
@@ -1,15 +1,13 @@
 #pragma once
 
-#include <unordered_map>
-
 #include <Core/Types.h>
+#include <Parsers/IAST_fwd.h>
+
+#include <unordered_map>
 
 namespace DB
 {
 
-class IAST;
-using ASTPtr = std::shared_ptr<IAST>;
-
 using Aliases = std::unordered_map<String, ASTPtr>;
 
 }
diff --git a/dbms/src/Interpreters/Context.h b/dbms/src/Interpreters/Context.h
index 8b4e66094fff162a7db2cf10e0af8cd084bdd103..4f90a50e349c09c26646fd9114ac102887b98487 100644
--- a/dbms/src/Interpreters/Context.h
+++ b/dbms/src/Interpreters/Context.h
@@ -1,23 +1,24 @@
 #pragma once
 
+#include <Core/Block.h>
+#include <Core/NamesAndTypes.h>
+#include <Core/Types.h>
+#include <Interpreters/ClientInfo.h>
+#include <Interpreters/Settings.h>
+#include <Parsers/IAST_fwd.h>
+#include <Common/LRUCache.h>
+#include <Common/MultiVersion.h>
+#include <Common/ThreadPool.h>
+#include <Common/config.h>
+
+#include <atomic>
 #include <chrono>
 #include <condition_variable>
 #include <functional>
 #include <memory>
 #include <mutex>
-#include <thread>
-#include <atomic>
 #include <optional>
-
-#include <Common/config.h>
-#include <Common/MultiVersion.h>
-#include <Common/LRUCache.h>
-#include <Common/ThreadPool.h>
-#include <Core/Types.h>
-#include <Core/NamesAndTypes.h>
-#include <Core/Block.h>
-#include <Interpreters/Settings.h>
-#include <Interpreters/ClientInfo.h>
+#include <thread>
 
 
 namespace Poco
@@ -68,8 +69,6 @@ class IStorage;
 class ITableFunction;
 using StoragePtr = std::shared_ptr<IStorage>;
 using Tables = std::map<String, StoragePtr>;
-class IAST;
-using ASTPtr = std::shared_ptr<IAST>;
 class IBlockInputStream;
 class IBlockOutputStream;
 using BlockInputStreamPtr = std::shared_ptr<IBlockInputStream>;
diff --git a/dbms/src/Interpreters/DatabaseAndTableWithAlias.h b/dbms/src/Interpreters/DatabaseAndTableWithAlias.h
index 0f1cbe8bbc7eaccb5ced97aabcd67016207f2748..22b03a5ed4464e95d6218d60f562981387164312 100644
--- a/dbms/src/Interpreters/DatabaseAndTableWithAlias.h
+++ b/dbms/src/Interpreters/DatabaseAndTableWithAlias.h
@@ -1,18 +1,16 @@
 #pragma once
 
+#include <Core/Names.h>
+#include <Core/Types.h>
+#include <Parsers/IAST_fwd.h>
+
 #include <memory>
 #include <optional>
 
-#include <Core/Types.h>
-#include <Core/Names.h>
-
 
 namespace DB
 {
 
-class IAST;
-using ASTPtr = std::shared_ptr<IAST>;
-
 class ASTSelectQuery;
 class ASTIdentifier;
 struct ASTTableExpression;
diff --git a/dbms/src/Interpreters/ExpressionAnalyzer.h b/dbms/src/Interpreters/ExpressionAnalyzer.h
index c7441efe4cb2b5d384ecbf774545468f8b12aacf..b9ec5c3ca70fda3c4953e72f527267841597317d 100644
--- a/dbms/src/Interpreters/ExpressionAnalyzer.h
+++ b/dbms/src/Interpreters/ExpressionAnalyzer.h
@@ -1,9 +1,11 @@
 #pragma once
 
+#include <Interpreters/ActionsVisitor.h>
 #include <Interpreters/AggregateDescription.h>
 #include <Interpreters/Settings.h>
-#include <Interpreters/ActionsVisitor.h>
 #include <Interpreters/SyntaxAnalyzer.h>
+#include <Parsers/IAST_fwd.h>
+
 
 namespace DB
 {
@@ -15,9 +17,6 @@ struct ExpressionActionsChain;
 class ExpressionActions;
 using ExpressionActionsPtr = std::shared_ptr<ExpressionActions>;
 
-class IAST;
-using ASTPtr = std::shared_ptr<IAST>;
-using ASTs = std::vector<ASTPtr>;
 struct ASTTableJoin;
 
 class IBlockInputStream;
diff --git a/dbms/src/Interpreters/InterpreterAlterQuery.h b/dbms/src/Interpreters/InterpreterAlterQuery.h
index bd9f3a89d6a8f43189ae8f65e264a15c9b2c32b2..776409a225d345c90e059349537d296b5fd1a694 100644
--- a/dbms/src/Interpreters/InterpreterAlterQuery.h
+++ b/dbms/src/Interpreters/InterpreterAlterQuery.h
@@ -1,14 +1,13 @@
 #pragma once
 
 #include <Interpreters/IInterpreter.h>
+#include <Parsers/IAST_fwd.h>
 
 
 namespace DB
 {
 
 class Context;
-class IAST;
-using ASTPtr = std::shared_ptr<IAST>;
 
 /** Allows you add or remove a column in the table.
   * It also allows you to manipulate the partitions of the MergeTree family tables.
diff --git a/dbms/src/Interpreters/InterpreterDescribeQuery.h b/dbms/src/Interpreters/InterpreterDescribeQuery.h
index fc0bea10f2d5617e46a716e955a8c8ba5c78c891..4fafe61f229ab2f55309d62bf984baf36d35a390 100644
--- a/dbms/src/Interpreters/InterpreterDescribeQuery.h
+++ b/dbms/src/Interpreters/InterpreterDescribeQuery.h
@@ -1,14 +1,13 @@
 #pragma once
 
 #include <Interpreters/IInterpreter.h>
+#include <Parsers/IAST_fwd.h>
 
 
 namespace DB
 {
 
 class Context;
-class IAST;
-using ASTPtr = std::shared_ptr<IAST>;
 
 
 /** Return names, types and other information about columns in specified table.
diff --git a/dbms/src/Interpreters/InterpreterDropQuery.h b/dbms/src/Interpreters/InterpreterDropQuery.h
index 2bea9f85c9995727f56d47d95885fd36bb3704da..1493d262a23a99acc7559aa37ae29b2c1334b6bc 100644
--- a/dbms/src/Interpreters/InterpreterDropQuery.h
+++ b/dbms/src/Interpreters/InterpreterDropQuery.h
@@ -1,16 +1,14 @@
 #pragma once
 
+#include <Databases/IDatabase.h>
 #include <Interpreters/IInterpreter.h>
 #include <Parsers/ASTDropQuery.h>
-#include <Databases/IDatabase.h>
-
+#include <Parsers/IAST_fwd.h>
 
 
 namespace DB
 {
 class Context;
-class IAST;
-using ASTPtr = std::shared_ptr<IAST>;
 using DatabaseAndTable = std::pair<DatabasePtr, StoragePtr>;
 
 /** Allow to either drop table with all its data (DROP),
diff --git a/dbms/src/Interpreters/InterpreterExistsQuery.h b/dbms/src/Interpreters/InterpreterExistsQuery.h
index b2050b443d85960e251516ba8c56cd05d02a5456..1860e1d0aa973a6e549f990f03fcc98ffd29868a 100644
--- a/dbms/src/Interpreters/InterpreterExistsQuery.h
+++ b/dbms/src/Interpreters/InterpreterExistsQuery.h
@@ -1,14 +1,13 @@
 #pragma once
 
 #include <Interpreters/IInterpreter.h>
+#include <Parsers/IAST_fwd.h>
 
 
 namespace DB
 {
 
 class Context;
-class IAST;
-using ASTPtr = std::shared_ptr<IAST>;
 
 
 /** Check that table exists. Return single row with single column "result" of type UInt8 and value 0 or 1.
diff --git a/dbms/src/Interpreters/InterpreterExplainQuery.h b/dbms/src/Interpreters/InterpreterExplainQuery.h
index 4db796ad0141b35f68c8280f2aae85bbba3b2b66..0d3b183857b90735d44a2f370a45890d97e91e4e 100644
--- a/dbms/src/Interpreters/InterpreterExplainQuery.h
+++ b/dbms/src/Interpreters/InterpreterExplainQuery.h
@@ -2,15 +2,12 @@
 
 #include <Interpreters/Context.h>
 #include <Interpreters/IInterpreter.h>
+#include <Parsers/IAST_fwd.h>
 
 
 namespace DB
 {
 
-class IAST;
-using ASTPtr = std::shared_ptr<IAST>;
-
-
 /// Returns single row with explain results
 class InterpreterExplainQuery : public IInterpreter
 {
diff --git a/dbms/src/Interpreters/InterpreterFactory.h b/dbms/src/Interpreters/InterpreterFactory.h
index 25bad6659d579f7564263b55b0c517eb459ebba0..1f065bbf69bb33d794a5e67efa5d69e2e8524766 100644
--- a/dbms/src/Interpreters/InterpreterFactory.h
+++ b/dbms/src/Interpreters/InterpreterFactory.h
@@ -2,14 +2,13 @@
 
 #include <Core/QueryProcessingStage.h>
 #include <Interpreters/IInterpreter.h>
+#include <Parsers/IAST_fwd.h>
 
 
 namespace DB
 {
 
 class Context;
-class IAST;
-using ASTPtr = std::shared_ptr<IAST>;
 
 
 class InterpreterFactory
diff --git a/dbms/src/Interpreters/InterpreterKillQueryQuery.h b/dbms/src/Interpreters/InterpreterKillQueryQuery.h
index 9294e45eab8ef253b65f65a99a656569afb7d56d..fab4b304865e8bf32f0542908a278f8264574b06 100644
--- a/dbms/src/Interpreters/InterpreterKillQueryQuery.h
+++ b/dbms/src/Interpreters/InterpreterKillQueryQuery.h
@@ -1,14 +1,13 @@
 #pragma once
 
 #include <Interpreters/IInterpreter.h>
+#include <Parsers/IAST.h>
 
 
 namespace DB
 {
 
 class Context;
-class IAST;
-using ASTPtr = std::shared_ptr<IAST>;
 
 
 class InterpreterKillQueryQuery : public IInterpreter
@@ -28,4 +27,3 @@ private:
 
 
 }
-
diff --git a/dbms/src/Interpreters/InterpreterOptimizeQuery.h b/dbms/src/Interpreters/InterpreterOptimizeQuery.h
index 03c369b0e4a98a7c69e0cefc792fe69597904d23..251d8ea02f3e54cacdee6477e1518f818a5a93ce 100644
--- a/dbms/src/Interpreters/InterpreterOptimizeQuery.h
+++ b/dbms/src/Interpreters/InterpreterOptimizeQuery.h
@@ -1,14 +1,13 @@
 #pragma once
 
 #include <Interpreters/IInterpreter.h>
+#include <Parsers/IAST_fwd.h>
 
 
 namespace DB
 {
 
 class Context;
-class IAST;
-using ASTPtr = std::shared_ptr<IAST>;
 
 
 /** Just call method "optimize" for table.
diff --git a/dbms/src/Interpreters/InterpreterRenameQuery.h b/dbms/src/Interpreters/InterpreterRenameQuery.h
index e9a36277ef0b49cdb0c187f8ce54474a4fcecb54..0433c638468bb871ab7b29c465e79fe2e34bc900 100644
--- a/dbms/src/Interpreters/InterpreterRenameQuery.h
+++ b/dbms/src/Interpreters/InterpreterRenameQuery.h
@@ -1,14 +1,13 @@
 #pragma once
 
 #include <Interpreters/IInterpreter.h>
+#include <Parsers/IAST_fwd.h>
 
 
 namespace DB
 {
 
 class Context;
-class IAST;
-using ASTPtr = std::shared_ptr<IAST>;
 
 
 /** Rename one table
diff --git a/dbms/src/Interpreters/InterpreterSelectQuery.cpp b/dbms/src/Interpreters/InterpreterSelectQuery.cpp
index 44b8f85a93236f4499e0cddeb8f68390eea8a8dd..70c256198895f04a54ae37ae72c1e5cb6ac93b1b 100644
--- a/dbms/src/Interpreters/InterpreterSelectQuery.cpp
+++ b/dbms/src/Interpreters/InterpreterSelectQuery.cpp
@@ -1078,7 +1078,8 @@ void InterpreterSelectQuery::executeFetchColumns(
 
 void InterpreterSelectQuery::executeWhere(Pipeline & pipeline, const ExpressionActionsPtr & expression, bool remove_fiter)
 {
-    pipeline.transform([&](auto & stream) {
+    pipeline.transform([&](auto & stream)
+    {
         stream = std::make_shared<FilterBlockInputStream>(
             stream, expression, query_ptr->as<ASTSelectQuery>()->where_expression->getColumnName(), remove_fiter);
     });
@@ -1206,7 +1207,8 @@ void InterpreterSelectQuery::executeMergeAggregated(Pipeline & pipeline, bool ov
 
 void InterpreterSelectQuery::executeHaving(Pipeline & pipeline, const ExpressionActionsPtr & expression)
 {
-    pipeline.transform([&](auto & stream) {
+    pipeline.transform([&](auto & stream)
+    {
         stream = std::make_shared<FilterBlockInputStream>(
             stream, expression, query_ptr->as<ASTSelectQuery>()->having_expression->getColumnName());
     });
diff --git a/dbms/src/Interpreters/InterpreterSetQuery.h b/dbms/src/Interpreters/InterpreterSetQuery.h
index 7dbd444f6f115c063a3053b1e3439215f9e71cec..434765cf7d0a433ef455a0520cd668af05185f3a 100644
--- a/dbms/src/Interpreters/InterpreterSetQuery.h
+++ b/dbms/src/Interpreters/InterpreterSetQuery.h
@@ -1,15 +1,14 @@
 #pragma once
 
 #include <Interpreters/IInterpreter.h>
+#include <Parsers/IAST_fwd.h>
 
 
 namespace DB
 {
 
 class Context;
-class IAST;
 class ASTSetQuery;
-using ASTPtr = std::shared_ptr<IAST>;
 
 
 /** Change one or several settings for the session or just for the current context.
diff --git a/dbms/src/Interpreters/InterpreterShowCreateQuery.h b/dbms/src/Interpreters/InterpreterShowCreateQuery.h
index 5e8672c17678e37fd984c79034d091e6af3bfb23..5ac98509b23496419d08b2fb05a201d7975ca8ee 100644
--- a/dbms/src/Interpreters/InterpreterShowCreateQuery.h
+++ b/dbms/src/Interpreters/InterpreterShowCreateQuery.h
@@ -1,14 +1,13 @@
 #pragma once
 
 #include <Interpreters/IInterpreter.h>
+#include <Parsers/IAST_fwd.h>
 
 
 namespace DB
 {
 
 class Context;
-class IAST;
-using ASTPtr = std::shared_ptr<IAST>;
 
 
 /** Return single row with single column "statement" of type String with text of query to CREATE specified table.
diff --git a/dbms/src/Interpreters/InterpreterShowProcesslistQuery.h b/dbms/src/Interpreters/InterpreterShowProcesslistQuery.h
index ee180e766994e67f355df561deff194e6245ea90..6b87fd7edc330f0323ec0fba31e331b2e2e3adc9 100644
--- a/dbms/src/Interpreters/InterpreterShowProcesslistQuery.h
+++ b/dbms/src/Interpreters/InterpreterShowProcesslistQuery.h
@@ -1,14 +1,13 @@
 #pragma once
 
 #include <Interpreters/IInterpreter.h>
+#include <Parsers/IAST_fwd.h>
 
 
 namespace DB
 {
 
 class Context;
-class IAST;
-using ASTPtr = std::shared_ptr<IAST>;
 
 
 /** Return list of currently executing queries.
diff --git a/dbms/src/Interpreters/InterpreterShowTablesQuery.h b/dbms/src/Interpreters/InterpreterShowTablesQuery.h
index 3f661da3e2d10506047cab36014edc4cd38949bf..fc5cb2b7505e012efef6723248cfdc361ca6a959 100644
--- a/dbms/src/Interpreters/InterpreterShowTablesQuery.h
+++ b/dbms/src/Interpreters/InterpreterShowTablesQuery.h
@@ -1,14 +1,13 @@
 #pragma once
 
 #include <Interpreters/IInterpreter.h>
+#include <Parsers/IAST_fwd.h>
 
 
 namespace DB
 {
 
 class Context;
-class IAST;
-using ASTPtr = std::shared_ptr<IAST>;
 
 
 /** Return a list of tables or databases meets specified conditions.
diff --git a/dbms/src/Interpreters/InterpreterSystemQuery.h b/dbms/src/Interpreters/InterpreterSystemQuery.h
index fb92e7997616f34ff8264bf6dc59f27faa4e8fad..65aaf7894190c81c79809315d48f53c9211aefaa 100644
--- a/dbms/src/Interpreters/InterpreterSystemQuery.h
+++ b/dbms/src/Interpreters/InterpreterSystemQuery.h
@@ -1,15 +1,15 @@
 #pragma once
+
 #include <Interpreters/IInterpreter.h>
+#include <Parsers/IAST_fwd.h>
 
 
 namespace DB
 {
 
 class Context;
-class IAST;
 class ASTSystemQuery;
 class IStorage;
-using ASTPtr = std::shared_ptr<IAST>;
 using StoragePtr = std::shared_ptr<IStorage>;
 
 
diff --git a/dbms/src/Interpreters/InterpreterUseQuery.h b/dbms/src/Interpreters/InterpreterUseQuery.h
index 988ccb741fae2e8525bcb6a7a8a5cc737010b52f..ae409117afd29540d09735d77392daa8dd4ffc60 100644
--- a/dbms/src/Interpreters/InterpreterUseQuery.h
+++ b/dbms/src/Interpreters/InterpreterUseQuery.h
@@ -1,14 +1,13 @@
 #pragma once
 
 #include <Interpreters/IInterpreter.h>
+#include <Parsers/IAST_fwd.h>
 
 
 namespace DB
 {
 
 class Context;
-class IAST;
-using ASTPtr = std::shared_ptr<IAST>;
 
 
 /** Change default database for session.
diff --git a/dbms/src/Storages/StorageMaterializedView.h b/dbms/src/Storages/StorageMaterializedView.h
index 8c2657b484bb69d17b067c036c8c9c1d3a52b4b6..665f6243a32c93a37c4eeee8fe8c21a176f5371a 100644
--- a/dbms/src/Storages/StorageMaterializedView.h
+++ b/dbms/src/Storages/StorageMaterializedView.h
@@ -2,16 +2,13 @@
 
 #include <ext/shared_ptr_helper.h>
 
+#include <Parsers/IAST_fwd.h>
 #include <Storages/IStorage.h>
 
 
 namespace DB
 {
 
-class IAST; // XXX: should include full class - for proper use inside inline methods
-using ASTPtr = std::shared_ptr<IAST>;
-
-
 class StorageMaterializedView : public ext::shared_ptr_helper<StorageMaterializedView>, public IStorage
 {
 public:
diff --git a/dbms/src/Storages/StorageView.h b/dbms/src/Storages/StorageView.h
index fed6664b8eb51327fef4e29cb5d03ad862d065d9..afd9b5ce326c76580bf91c6430b9d34a0beb9f5c 100644
--- a/dbms/src/Storages/StorageView.h
+++ b/dbms/src/Storages/StorageView.h
@@ -1,17 +1,15 @@
 #pragma once
 
-#include <ext/shared_ptr_helper.h>
-#include <Storages/IStorage.h>
 #include <Parsers/ASTSelectQuery.h>
+#include <Parsers/IAST_fwd.h>
+#include <Storages/IStorage.h>
+
+#include <ext/shared_ptr_helper.h>
 
 
 namespace DB
 {
 
-class IAST;
-using ASTPtr = std::shared_ptr<IAST>;
-
-
 class StorageView : public ext::shared_ptr_helper<StorageView>, public IStorage
 {
 public:
diff --git a/dbms/src/TableFunctions/ITableFunction.h b/dbms/src/TableFunctions/ITableFunction.h
index ddf900fa65cf9cca04ce56e21556167692b1db90..39ef7857a3ab4534f810b196aef36bc6f5d745e9 100644
--- a/dbms/src/TableFunctions/ITableFunction.h
+++ b/dbms/src/TableFunctions/ITableFunction.h
@@ -1,14 +1,15 @@
 #pragma once
 
+#include <Parsers/IAST_fwd.h>
+
 #include <string>
 #include <memory>
 
+
 namespace DB
 {
 
 class Context;
-class IAST;
-using ASTPtr = std::shared_ptr<IAST>;
 class IStorage;
 using StoragePtr = std::shared_ptr<IStorage>;