Merge pull request #10563 from azat/SELECT-ALIAS-CAST

Fix SELECT of column ALIAS which default expression type different from column type
ClickHouse · May 11, 2020 · 15e38c8 · 15e38c8
2 parents 6149638 + d2c813f
commit 15e38c8
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Showing 3 changed files with 33 additions and 1 deletion.
diff --git a/src/Interpreters/InterpreterSelectQuery.cpp b/src/Interpreters/InterpreterSelectQuery.cpp
@@ -44,6 +44,7 @@
 #include <Interpreters/InterpreterSetQuery.h>
 #include <Interpreters/evaluateConstantExpression.h>
 #include <Interpreters/convertFieldToType.h>
+#include <Interpreters/addTypeConversionToAST.h>
 #include <Interpreters/ExpressionAnalyzer.h>
 #include <Interpreters/getTableExpressions.h>
 #include <Interpreters/JoinToSubqueryTransformVisitor.h>
@@ -1210,7 +1211,12 @@ void InterpreterSelectQuery::executeFetchColumns(
                 const auto column_default = storage_columns.getDefault(column);
                 bool is_alias = column_default && column_default->kind == ColumnDefaultKind::Alias;
                 if (is_alias)
-                    column_expr = setAlias(column_default->expression->clone(), column);
+                {
+                    auto column_decl = storage_columns.get(column);
+                    /// TODO: can make CAST only if the type is different (but requires SyntaxAnalyzer).
+                    auto cast_column_default = addTypeConversionToAST(column_default->expression->clone(), column_decl.type->getName());
+                    column_expr = setAlias(cast_column_default->clone(), column);
+                }
                 else
                     column_expr = std::make_shared<ASTIdentifier>(column);
 

diff --git a/tests/queries/0_stateless/01269_alias_type_differs.reference b/tests/queries/0_stateless/01269_alias_type_differs.reference
@@ -0,0 +1,4 @@
+UInt8
+0
+UInt8
+0
diff --git a/tests/queries/0_stateless/01269_alias_type_differs.sql b/tests/queries/0_stateless/01269_alias_type_differs.sql
@@ -0,0 +1,22 @@
+DROP TABLE IF EXISTS data_01269;
+CREATE TABLE data_01269
+(
+    key     Int32,
+    value   Nullable(Int32),
+    alias   UInt8 ALIAS value>0
+)
+ENGINE = MergeTree()
+ORDER BY key;
+INSERT INTO data_01269 VALUES (1, 0);
+
+-- after PR#10441
+SELECT toTypeName(alias) FROM data_01269;
+SELECT any(alias) FROM data_01269;
+
+-- even without PR#10441
+ALTER TABLE data_01269 DROP COLUMN alias;
+ALTER TABLE data_01269 ADD COLUMN alias UInt8 ALIAS value>0;
+SELECT toTypeName(alias) FROM data_01269;
+SELECT any(alias) FROM data_01269;
+
+DROP TABLE data_01269;