ClickHouse/dbms/src/Interpreters/addMissingDefaults.cpp

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#include <Interpreters/addMissingDefaults.h>
#include <Common/typeid_cast.h>
#include <DataTypes/NestedUtils.h>
#include <DataTypes/DataTypeArray.h>
#include <Columns/ColumnArray.h>
#include <Interpreters/evaluateMissingDefaults.h>
#include <Core/Block.h>
#include <Storages/ColumnDefault.h>
namespace DB
{
Block addMissingDefaults(const Block & block,
const NamesAndTypesList & required_columns,
const ColumnDefaults & column_defaults,
const Context & context)
{
/// For missing columns of nested structure, you need to create not a column of empty arrays, but a column of arrays of correct lengths.
/// First, remember the offset columns for all arrays in the block.
std::map<String, ColumnPtr> offset_columns;
for (size_t i = 0, size = block.columns(); i < size; ++i)
{
const auto & elem = block.getByPosition(i);
if (const ColumnArray * array = typeid_cast<const ColumnArray *>(&*elem.column))
{
String offsets_name = Nested::extractTableName(elem.name);
auto & offsets_column = offset_columns[offsets_name];
/// If for some reason there are different offset columns for one nested structure, then we take nonempty.
if (!offsets_column || offsets_column->empty())
offsets_column = array->getOffsetsPtr();
}
}
const size_t rows = block.rows();
Block res;
/// We take given columns from input block and missed columns without default value
/// (default and materialized will be computed later).
for (const auto & column : required_columns)
{
if (block.has(column.name))
{
res.insert(block.getByName(column.name));
continue;
}
if (column_defaults.count(column.name))
continue;
String offsets_name = Nested::extractTableName(column.name);
if (offset_columns.count(offsets_name))
{
ColumnPtr offsets_column = offset_columns[offsets_name];
DataTypePtr nested_type = typeid_cast<const DataTypeArray &>(*column.type).getNestedType();
UInt64 nested_rows = rows ? get<UInt64>((*offsets_column)[rows - 1]) : 0;
ColumnPtr nested_column = nested_type->createColumnConstWithDefaultValue(nested_rows)->convertToFullColumnIfConst();
auto new_column = ColumnArray::create(nested_column, offsets_column);
res.insert(ColumnWithTypeAndName(std::move(new_column), column.type, column.name));
continue;
}
/** It is necessary to turn a constant column into a full column, since in part of blocks (from other parts),
* it can be full (or the interpreter may decide that it is constant everywhere).
*/
auto new_column = column.type->createColumnConstWithDefaultValue(rows)->convertToFullColumnIfConst();
res.insert(ColumnWithTypeAndName(std::move(new_column), column.type, column.name));
}
/// Computes explicitly specified values (in column_defaults) by default and materialized columns.
evaluateMissingDefaults(res, required_columns, column_defaults, context);
return res;
}
}