ClickHouse/src/Analyzer/ColumnNode.h

#pragma once

#include <Core/NamesAndTypes.h>

#include <Analyzer/IQueryTreeNode.h>

namespace DB
{

/** Column node represents column in query tree.
  * Column must have some column source.
  * Column can be table expression, lambda, subquery.
  * Column source must be valid during column node lifetime.
  *
  * For table ALIAS columns. Column node must contain expression.
  * For ARRAY JOIN join expression column. Column node must contain expression.
  *
  * During query analysis pass identifier node is resolved into column. See IdentifierNode.h.
  *
  * It is also important for client provide display identifier for AST conversion in case of JOINS are used.
  * Example: SELECT t1.id, t2.id FROM test_table_1 AS t1, test_table_2 AS t2.
  * In this example t1.id will be column with name id, but during conversion to AST, to keep AST valid it is important
  * to save column name qualification. Display identifier does not take part in implementation of tree hash,
  * or tree equals operator. It is only used during AST conversion.
  *
  * Examples:
  * SELECT id FROM test_table. id is identifier that must be resolved to column node during query analysis pass.
  * SELECT lambda(x -> x + 1, [1,2,3]). x is identifier inside lambda that must be resolved to column node during query analysis pass.
  *
  * Column node is initialized with column name, type and column source weak pointer.
  * In case of ALIAS column node is initialized with column name, type, alias expression and column source weak pointer.
  *
  * Additional care must be taken during clone to repoint column source to another node if its necessary see IQueryTreeNode.h `clone` method.
  */
class ColumnNode;
using ColumnNodePtr = std::shared_ptr<ColumnNode>;

class ColumnNode final : public IQueryTreeNode
{
public:
    /// Construct column node with column name, type and column source weak pointer.
    ColumnNode(NameAndTypePair column_, QueryTreeNodeWeakPtr column_source_);

    /// Construct expression column node with column name, type, column expression and column source weak pointer.
    ColumnNode(NameAndTypePair column_, QueryTreeNodePtr expression_node_, QueryTreeNodeWeakPtr column_source_);

    /// Get column
    const NameAndTypePair & getColumn() const
    {
        return column;
    }

    /// Get column name
    const String & getColumnName() const
    {
        return column.name;
    }

    /// Set display identifier that will be used during convertion to AST
    void setDisplayIdentifier(const Identifier & display_identifier_value)
    {
        display_identifier = display_identifier_value;
    }

    const Identifier & getDisplayIdentifier() const
    {
        return display_identifier;
    }

    /// Get column type
    const DataTypePtr & getColumnType() const
    {
        return column.type;
    }

    /// Set column type
    void setColumnType(DataTypePtr column_type)
    {
        column.type = std::move(column_type);
    }

    bool hasExpression() const
    {
        return children[expression_child_index] != nullptr;
    }

    const QueryTreeNodePtr & getExpression() const
    {
        return children[expression_child_index];
    }

    QueryTreeNodePtr & getExpression()
    {
        return children[expression_child_index];
    }

    QueryTreeNodePtr & getExpressionOrThrow()
    {
        if (!children[expression_child_index])
            throw Exception(ErrorCodes::LOGICAL_ERROR, "Column expression is not initialized");

        return children[expression_child_index];
    }

    void setExpression(QueryTreeNodePtr expression_value)
    {
        children[expression_child_index] = std::move(expression_value);
    }

    /** Get column source.
      * If column source is not valid logical exception is thrown.
      */
    QueryTreeNodePtr getColumnSource() const;

    /// Get column source weak pointer
    QueryTreeNodeWeakPtr getColumnSourceWeak() const
    {
        return column_source;
    }

    QueryTreeNodeType getNodeType() const override
    {
        return QueryTreeNodeType::COLUMN;
    }

    String getName() const override
    {
        return column.name;
    }

    DataTypePtr getResultType() const override
    {
        return column.type;
    }

    void dumpTreeImpl(WriteBuffer & buffer, FormatState & state, size_t indent) const override;

    bool isEqualImpl(const IQueryTreeNode & rhs) const override;

    void updateTreeHashImpl(HashState & hash_state) const override;

protected:
    ASTPtr toASTImpl() const override;

    QueryTreeNodePtr cloneImpl() const override;

    void getPointersToUpdateAfterClone(QueryTreePointersToUpdate & pointers_to_update) override;

private:
    NameAndTypePair column;
    QueryTreeNodeWeakPtr column_source;
    Identifier display_identifier;

    static constexpr size_t expression_child_index = 0;
    static constexpr size_t children_size = expression_child_index + 1;
};

}