ClickHouse/src/Interpreters/getTableExpressions.cpp

#include <Interpreters/getTableExpressions.h>
#include <Interpreters/InterpreterSelectWithUnionQuery.h>
#include <Parsers/ASTTablesInSelectQuery.h>
#include <Parsers/ASTSelectQuery.h>
#include <Storages/IStorage.h>

namespace DB
{

NameSet removeDuplicateColumns(NamesAndTypesList & columns)
{
    NameSet names;
    for (auto it = columns.begin(); it != columns.end();)
    {
        if (names.emplace(it->name).second)
            ++it;
        else
            columns.erase(it++);
    }
    return names;
}

std::vector<const ASTTableExpression *> getTableExpressions(const ASTSelectQuery & select_query)
{
    if (!select_query.tables())
        return {};

    std::vector<const ASTTableExpression *> tables_expression;

    for (const auto & child : select_query.tables()->children)
    {
        const auto * tables_element = child->as<ASTTablesInSelectQueryElement>();

        if (tables_element && tables_element->table_expression)
            tables_expression.emplace_back(tables_element->table_expression->as<ASTTableExpression>());
    }

    return tables_expression;
}

const ASTTableExpression * getTableExpression(const ASTSelectQuery & select, size_t table_number)
{
    if (!select.tables())
        return {};

    const auto & tables_in_select_query = select.tables()->as<ASTTablesInSelectQuery &>();
    if (tables_in_select_query.children.size() <= table_number)
        return {};

    const auto & tables_element = tables_in_select_query.children[table_number]->as<ASTTablesInSelectQueryElement &>();

    if (!tables_element.table_expression)
        return {};

    return tables_element.table_expression->as<ASTTableExpression>();
}

ASTPtr extractTableExpression(const ASTSelectQuery & select, size_t table_number)
{
    if (const ASTTableExpression * table_expression = getTableExpression(select, table_number))
    {
        if (table_expression->database_and_table_name)
            return table_expression->database_and_table_name;

        if (table_expression->table_function)
            return table_expression->table_function;

        if (table_expression->subquery)
            return table_expression->subquery->children[0];
    }

    return nullptr;
}

static NamesAndTypesList getColumnsFromTableExpression(const ASTTableExpression & table_expression, const Context & context,
                                                NamesAndTypesList & materialized, NamesAndTypesList & aliases, NamesAndTypesList & virtuals)
{
    NamesAndTypesList names_and_type_list;
    if (table_expression.subquery)
    {
        const auto & subquery = table_expression.subquery->children.at(0);
        names_and_type_list = InterpreterSelectWithUnionQuery::getSampleBlock(subquery, context).getNamesAndTypesList();
    }
    else if (table_expression.table_function)
    {
        const auto table_function = table_expression.table_function;
        auto query_context = const_cast<Context *>(&context.getQueryContext());
        const auto & function_storage = query_context->executeTableFunction(table_function);
        auto & columns = function_storage->getColumns();
        names_and_type_list = columns.getOrdinary();
        materialized = columns.getMaterialized();
        aliases = columns.getAliases();
        virtuals = columns.getVirtuals();
    }
    else if (table_expression.database_and_table_name)
    {
        auto table_id = context.resolveStorageID(table_expression.database_and_table_name);
        const auto & table = DatabaseCatalog::instance().getTable(table_id);
        auto & columns = table->getColumns();
        names_and_type_list = columns.getOrdinary();
        materialized = columns.getMaterialized();
        aliases = columns.getAliases();
        virtuals = columns.getVirtuals();
    }

    return names_and_type_list;
}

NamesAndTypesList getColumnsFromTableExpression(const ASTTableExpression & table_expression, const Context & context)
{
    NamesAndTypesList materialized;
    NamesAndTypesList aliases;
    NamesAndTypesList virtuals;
    return getColumnsFromTableExpression(table_expression, context, materialized, aliases, virtuals);
}

std::vector<TableWithColumnNamesAndTypes> getDatabaseAndTablesWithColumns(const std::vector<const ASTTableExpression *> & table_expressions,
                                                                          const Context & context)
{
    std::vector<TableWithColumnNamesAndTypes> tables_with_columns;

    if (!table_expressions.empty())
    {
        String current_database = context.getCurrentDatabase();

        for (const ASTTableExpression * table_expression : table_expressions)
        {
            NamesAndTypesList materialized;
            NamesAndTypesList aliases;
            NamesAndTypesList virtuals;
            NamesAndTypesList names_and_types = getColumnsFromTableExpression(*table_expression, context, materialized, aliases, virtuals);

            removeDuplicateColumns(names_and_types);

            tables_with_columns.emplace_back(
                DatabaseAndTableWithAlias(*table_expression, current_database), names_and_types);

            auto & table = tables_with_columns.back();
            table.addHiddenColumns(materialized);
            table.addHiddenColumns(aliases);
            table.addHiddenColumns(virtuals);
        }
    }

    return tables_with_columns;
}

std::vector<TableWithColumnNames> getDatabaseAndTablesWithColumnNames(const std::vector<const ASTTableExpression *> & table_expressions,
                                                                      const Context & context)
{
    std::vector<TableWithColumnNamesAndTypes> tables_with_columns = getDatabaseAndTablesWithColumns(table_expressions, context);
    std::vector<TableWithColumnNames> out;
    out.reserve(tables_with_columns.size());
    for (auto & table : tables_with_columns)
        out.emplace_back(table.removeTypes());
    return out;
}

}