ClickHouse/dbms/src/Storages/StorageView.cpp

#include <Interpreters/InterpreterSelectQuery.h>
#include <Parsers/ASTIdentifier.h>
#include <Parsers/ASTCreateQuery.h>
#include <Parsers/ASTSelectQuery.h>

#include <Storages/StorageView.h>


namespace DB
{

namespace ErrorCodes
{
    extern const int LOGICAL_ERROR;
}


StorageView::StorageView(
    const String & table_name_,
    const String & database_name_,
    Context & context_,
    ASTPtr & query_,
    NamesAndTypesListPtr columns_,
    const NamesAndTypesList & materialized_columns_,
    const NamesAndTypesList & alias_columns_,
    const ColumnDefaults & column_defaults_)
    : IStorage{materialized_columns_, alias_columns_, column_defaults_}, table_name(table_name_),
    database_name(database_name_), context(context_), columns(columns_)
{
    ASTCreateQuery & create = typeid_cast<ASTCreateQuery &>(*query_);
    ASTSelectQuery & select = typeid_cast<ASTSelectQuery &>(*create.select);

    /// If the internal query does not specify a database, retrieve it from the context and write it to the query.
    select.setDatabaseIfNeeded(database_name);

    inner_query = select;

    extractDependentTable(inner_query);

    if (!select_table_name.empty())
        context.getGlobalContext().addDependency(
            DatabaseAndTableName(select_database_name, select_table_name),
            DatabaseAndTableName(database_name, table_name));
}


void StorageView::extractDependentTable(const ASTSelectQuery & query)
{
    auto query_table = query.table();

    if (!query_table)
        return;

    if (const ASTIdentifier * ast_id = typeid_cast<const ASTIdentifier *>(query_table.get()))
    {
        auto query_database = query.database();

        if (!query_database)
            throw Exception("Logical error while creating StorageView."
                " Could not retrieve database name from select query.",
                DB::ErrorCodes::LOGICAL_ERROR);

        select_database_name = typeid_cast<const ASTIdentifier &>(*query_database).name;
        select_table_name = ast_id->name;
    }
    else if (const ASTSelectQuery * ast_select = typeid_cast<const ASTSelectQuery *>(query_table.get()))
    {
        extractDependentTable(*ast_select);
    }
    else
        throw Exception("Logical error while creating StorageView."
            " Could not retrieve table name from select query.",
            DB::ErrorCodes::LOGICAL_ERROR);
}


BlockInputStreams StorageView::read(
    const Names & column_names,
    const ASTPtr & query,
    const Context & context,
    QueryProcessingStage::Enum & processed_stage,
    const size_t max_block_size,
    const unsigned num_streams)
{
    processed_stage = QueryProcessingStage::FetchColumns;
    ASTPtr inner_query_clone = getInnerQuery();
    return InterpreterSelectQuery(inner_query_clone, context, column_names).executeWithoutUnion();
}


void StorageView::drop()
{
    if (!select_table_name.empty())
        context.getGlobalContext().removeDependency(
            DatabaseAndTableName(select_database_name, select_table_name),
            DatabaseAndTableName(database_name, table_name));
}


}