Added method "getHeader" in IBlockOutputStream: development [#CLICKHOUSE-2]

dbms/src/DataStreams/AddingDefaultBlockOutputStream.cpp

@@ -71,9 +71,6 @@ void AddingDefaultBlockOutputStream::write(const Block & block)
     }
 
     /// Computes explicitly specified values (in column_defaults) by default.
-    /** @todo if somehow block does not contain values for implicitly-defaulted columns that are prerequisites
-         *    for explicitly-defaulted ones, exception will be thrown during evaluating such columns
-         *    (implicitly-defaulted columns are evaluated on the line after following one. */
     evaluateMissingDefaults(res, required_columns, column_defaults, context);
 
     output->write(res);

dbms/src/Interpreters/ExpressionActions.cpp

@@ -142,39 +142,11 @@ ExpressionAction ExpressionAction::ordinaryJoin(std::shared_ptr<const Join> join
 }
 
 
-ExpressionActions::Actions ExpressionAction::getPrerequisites(Block & sample_block)
-{
-    ExpressionActions::Actions res;
-
-    if (type == APPLY_FUNCTION)
-    {
-        if (sample_block.has(result_name))
-            throw Exception("Column '" + result_name + "' already exists", ErrorCodes::DUPLICATE_COLUMN);
-
-        ColumnsWithTypeAndName arguments(argument_names.size());
-        for (size_t i = 0; i < argument_names.size(); ++i)
-        {
-            if (!sample_block.has(argument_names[i]))
-                throw Exception("Unknown identifier: '" + argument_names[i] + "'", ErrorCodes::UNKNOWN_IDENTIFIER);
-            arguments[i] = sample_block.getByName(argument_names[i]);
-        }
-
-        function = function_builder->build(arguments);
-        result_type = function->getReturnType();
-    }
-
-    return res;
-}
-
 void ExpressionAction::prepare(Block & sample_block)
 {
 //    std::cerr << "preparing: " << toString() << std::endl;
 
     /** Constant expressions should be evaluated, and put the result in sample_block.
-      * For non-constant columns, put the nullptr as the column in sample_block.
-      *
-      * The fact that only for constant expressions column != nullptr,
-      *  can be used later when optimizing the query.
       */
 
     switch (type)
@@ -567,40 +539,43 @@ void ExpressionActions::addInput(const NameAndTypePair & column)
 
 void ExpressionActions::add(const ExpressionAction & action, Names & out_new_columns)
 {
-    NameSet temp_names;
-    addImpl(action, temp_names, out_new_columns);
+    addImpl(action, out_new_columns);
 }
 
 void ExpressionActions::add(const ExpressionAction & action)
 {
-    NameSet temp_names;
     Names new_names;
-    addImpl(action, temp_names, new_names);
+    addImpl(action, new_names);
 }
 
-void ExpressionActions::addImpl(ExpressionAction action, NameSet & current_names, Names & new_names)
+void ExpressionActions::addImpl(ExpressionAction action, Names & new_names)
 {
     if (sample_block.has(action.result_name))
         return;
 
-    if (current_names.count(action.result_name))
-        throw Exception("Cyclic function prerequisites: " + action.result_name, ErrorCodes::LOGICAL_ERROR);
-
-    current_names.insert(action.result_name);
-
     if (action.result_name != "")
         new_names.push_back(action.result_name);
     new_names.insert(new_names.end(), action.array_joined_columns.begin(), action.array_joined_columns.end());
 
-    Actions prerequisites = action.getPrerequisites(sample_block);
+    if (action.type == ExpressionAction::APPLY_FUNCTION)
+    {
+        if (sample_block.has(action.result_name))
+            throw Exception("Column '" + action.result_name + "' already exists", ErrorCodes::DUPLICATE_COLUMN);
 
-    for (size_t i = 0; i < prerequisites.size(); ++i)
-        addImpl(prerequisites[i], current_names, new_names);
+        ColumnsWithTypeAndName arguments(action.argument_names.size());
+        for (size_t i = 0; i < action.argument_names.size(); ++i)
+        {
+            if (!sample_block.has(action.argument_names[i]))
+                throw Exception("Unknown identifier: '" + action.argument_names[i] + "'", ErrorCodes::UNKNOWN_IDENTIFIER);
+            arguments[i] = sample_block.getByName(action.argument_names[i]);
+        }
+
+        action.function = action.function_builder->build(arguments);
+        action.result_type = action.function->getReturnType();
+    }
 
     action.prepare(sample_block);
     actions.push_back(action);
-
-    current_names.erase(action.result_name);
 }
 
 void ExpressionActions::prependProjectInput()

dbms/src/Interpreters/ExpressionActions.h

@@ -99,7 +99,6 @@ public:
     static ExpressionAction ordinaryJoin(std::shared_ptr<const Join> join_, const NamesAndTypesList & columns_added_by_join_);
 
     /// Which columns necessary to perform this action.
-    /// If this `Action` is not already added to `ExpressionActions`, the returned list may be incomplete, because `prerequisites` are not taken into account.
     Names getNeededColumns() const;
 
     std::string toString() const;
@@ -107,7 +106,6 @@ public:
 private:
     friend class ExpressionActions;
 
-    std::vector<ExpressionAction> getPrerequisites(Block & sample_block);
     void prepare(Block & sample_block);
     void execute(Block & block) const;
     void executeOnTotals(Block & block) const;
@@ -147,8 +145,7 @@ public:
 
     void add(const ExpressionAction & action);
 
-    /// Adds new column names to out_new_columns
-    ///  (formed as a result of the added action and its prerequisites).
+    /// Adds new column names to out_new_columns (formed as a result of the added action).
     void add(const ExpressionAction & action, Names & out_new_columns);
 
     /// Adds to the beginning the removal of all extra columns.
@@ -208,9 +205,7 @@ private:
 
     void checkLimits(Block & block) const;
 
-    /// Adds all `prerequisites` first, then the action itself.
-    /// current_names - columns whose `prerequisites` are currently being processed.
-    void addImpl(ExpressionAction action, NameSet & current_names, Names & new_names);
+    void addImpl(ExpressionAction action, Names & new_names);
 
     /// Try to improve something without changing the lists of input and output columns.
     void optimize();

dbms/src/Interpreters/ExpressionAnalyzer.cpp

@@ -2653,7 +2653,13 @@ Block ExpressionAnalyzer::getSelectSampleBlock()
 
     temp_actions->add(ExpressionAction::project(result_columns));
 
-    return temp_actions->getSampleBlock();
+    Block res = temp_actions->getSampleBlock();
+
+    for (auto & elem : res)
+        if (!elem.column)
+            elem.column = elem.type->createColumn();
+
+    return res;
 }
 
 void ExpressionAnalyzer::getActionsBeforeAggregation(const ASTPtr & ast, ExpressionActionsPtr & actions, bool no_subqueries)

dbms/src/Interpreters/InterpreterSelectQuery.cpp

@@ -374,15 +374,7 @@ DataTypes InterpreterSelectQuery::getReturnTypes()
 
 Block InterpreterSelectQuery::getSampleBlock()
 {
-    Block block = query_analyzer->getSelectSampleBlock();
-    /// create non-zero columns so that SampleBlock can be
-    /// written (read) with BlockOut(In)putStreams
-    for (size_t i = 0; i < block.columns(); ++i)
-    {
-        ColumnWithTypeAndName & col = block.safeGetByPosition(i);
-        col.column = col.type->createColumn();
-    }
-    return block;
+    return query_analyzer->getSelectSampleBlock();
 }