Method getSampleBlock

src/Interpreters/InterpreterInsertQuery.cpp:256–298

}

Block InterpreterInsertQuery::getSampleBlock(
    const ASTInsertQuery & query, const StoragePtr & table, const StorageMetadataPtr & metadata_snapshot) const
{
    /// If the query does not include information about columns
    if (!query.columns)
    {
        if (no_destination)
            return metadata_snapshot->getSampleBlockWithVirtuals(table->getVirtuals());
        else
            return metadata_snapshot->getSampleBlockNonMaterialized();
    }

    Block table_sample_non_materialized;
    if (no_destination)
        table_sample_non_materialized = metadata_snapshot->getSampleBlockWithVirtuals(table->getVirtuals());
    else
        table_sample_non_materialized = metadata_snapshot->getSampleBlockNonMaterialized(/*include_func_columns*/ true);

    Block table_sample = metadata_snapshot->getSampleBlock(/*include_func_columns*/ true);

    const auto columns_ast = processColumnTransformers(getContext()->getCurrentDatabase(), table, metadata_snapshot, query.columns);

    /// Form the block based on the column names from the query
    Block res;
    for (const auto & identifier : columns_ast->children)
    {
        std::string current_name = identifier->getColumnName();

        /// The table does not have a column with that name
        if (!table_sample.has(current_name))
            throw Exception(
                "No such column " + current_name + " in table " + table->getStorageID().getNameForLogs(),
                ErrorCodes::NO_SUCH_COLUMN_IN_TABLE);

        if (!allow_materialized && !table_sample_non_materialized.has(current_name))
            throw Exception("Cannot insert column " + current_name + ", because it is MATERIALIZED column.", ErrorCodes::ILLEGAL_COLUMN);
        if (res.has(current_name))
            throw Exception("Column " + current_name + " specified more than once", ErrorCodes::DUPLICATE_COLUMN);

        res.insert(ColumnWithTypeAndName(table_sample.getByName(current_name).type, current_name));
    }
    return res;
}


/** A query that just reads all data without any complex computations or filetering.