ClickHouse/src/Interpreters/ExtractExpressionInfoVisitor.cpp

#include <Interpreters/ExtractExpressionInfoVisitor.h>
#include <Functions/FunctionFactory.h>
#include <AggregateFunctions/AggregateFunctionFactory.h>
#include <Interpreters/IdentifierSemantic.h>
#include <Parsers/ASTSubquery.h>


namespace DB
{

void ExpressionInfoMatcher::visit(const ASTPtr & ast, Data & data)
{
    if (const auto * function = ast->as<ASTFunction>())
        visit(*function, ast, data);
    else if (const auto * identifier = ast->as<ASTIdentifier>())
        visit(*identifier, ast, data);
}

void ExpressionInfoMatcher::visit(const ASTFunction & ast_function, const ASTPtr &, Data & data)
{
    if (ast_function.name == "arrayJoin")
    {
        data.is_array_join = true;
    }
    // "is_aggregate_function" doesn't mean much by itself. Apparently here it is
    // used to move filters from HAVING to WHERE, and probably for this purpose
    // an aggregate function calculated as a window function is not relevant.
    else if (!ast_function.is_window_function
        && AggregateFunctionFactory::instance().isAggregateFunctionName(
            ast_function.name))
    {
        data.is_aggregate_function = true;
    }
    else
    {
        const auto & function = FunctionFactory::instance().tryGet(ast_function.name, data.context);

        /// Skip lambda, tuple and other special functions
        if (function)
        {
            if (function->isStateful())
                data.is_stateful_function = true;

            if (!function->isDeterministicInScopeOfQuery())
                data.is_deterministic_function = false;
        }
    }
}

void ExpressionInfoMatcher::visit(const ASTIdentifier & identifier, const ASTPtr &, Data & data)
{
    if (!identifier.compound())
    {
        for (size_t index = 0; index < data.tables.size(); ++index)
        {
            const auto & table = data.tables[index];

            // TODO: make sure no collision ever happens
            if (table.hasColumn(identifier.name()))
            {
                data.unique_reference_tables_pos.emplace(index);
                break;
            }
        }
    }
    else
    {
        if (auto best_table_pos = IdentifierSemantic::chooseTable(identifier, data.tables))
            data.unique_reference_tables_pos.emplace(*best_table_pos);
    }
}

bool ExpressionInfoMatcher::needChildVisit(const ASTPtr & node, const ASTPtr &)
{
    return !node->as<ASTSubquery>();
}

bool hasStatefulFunction(const ASTPtr & node, const Context & context)
{
    for (const auto & select_expression : node->children)
    {
        ExpressionInfoVisitor::Data expression_info{.context = context, .tables = {}};
        ExpressionInfoVisitor(expression_info).visit(select_expression);

        if (expression_info.is_stateful_function)
            return true;
    }

    return false;
}

}