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#include <Storages/IStorage.h>
#include <Processors/Sources/SourceFromSingleChunk.h>
#include <QueryPipeline/BlockIO.h>
#include <DataTypes/DataTypeString.h>
#include <Parsers/queryToString.h>
#include <Common/typeid_cast.h>
#include <TableFunctions/ITableFunction.h>
#include <TableFunctions/TableFunctionFactory.h>
#include <Interpreters/InterpreterSelectWithUnionQuery.h>
#include <Interpreters/InterpreterSelectQueryAnalyzer.h>
#include <Interpreters/Context.h>
#include <Interpreters/InterpreterDescribeQuery.h>
#include <Interpreters/IdentifierSemantic.h>
#include <Access/Common/AccessFlags.h>
#include <Parsers/ASTIdentifier.h>
#include <Parsers/ASTFunction.h>
#include <Parsers/ASTTablesInSelectQuery.h>
#include <Parsers/TablePropertiesQueriesASTs.h>
#include <DataTypes/NestedUtils.h>
namespace DB
{
Block InterpreterDescribeQuery::getSampleBlock(bool include_subcolumns)
{
Block block;
ColumnWithTypeAndName col;
col.name = "name";
col.type = std::make_shared<DataTypeString>();
col.column = col.type->createColumn();
block.insert(col);
col.name = "type";
block.insert(col);
col.name = "default_type";
block.insert(col);
col.name = "default_expression";
block.insert(col);
col.name = "comment";
block.insert(col);
col.name = "codec_expression";
block.insert(col);
col.name = "ttl_expression";
block.insert(col);
if (include_subcolumns)
{
col.name = "is_subcolumn";
col.type = std::make_shared<DataTypeUInt8>();
col.column = col.type->createColumn();
block.insert(col);
}
return block;
}
BlockIO InterpreterDescribeQuery::execute()
{
std::vector<ColumnDescription> columns;
StorageSnapshotPtr storage_snapshot;
const auto & ast = query_ptr->as<ASTDescribeQuery &>();
const auto & table_expression = ast.table_expression->as<ASTTableExpression &>();
const auto & settings = getContext()->getSettingsRef();
if (table_expression.subquery)
{
NamesAndTypesList names_and_types;
auto select_query = table_expression.subquery->children.at(0);
auto current_context = getContext();
if (settings.allow_experimental_analyzer)
{
SelectQueryOptions select_query_options;
names_and_types = InterpreterSelectQueryAnalyzer(select_query, current_context, select_query_options).getSampleBlock().getNamesAndTypesList();
}
else
{
names_and_types = InterpreterSelectWithUnionQuery::getSampleBlock(select_query, current_context).getNamesAndTypesList();
}
for (auto && [name, type] : names_and_types)
{
ColumnDescription description;
description.name = std::move(name);
description.type = std::move(type);
columns.emplace_back(std::move(description));
}
}
else if (table_expression.table_function)
{
TableFunctionPtr table_function_ptr = TableFunctionFactory::instance().get(table_expression.table_function, getContext());
auto table_function_column_descriptions = table_function_ptr->getActualTableStructure(getContext(), /*is_insert_query*/ true);
for (const auto & table_function_column_description : table_function_column_descriptions)
columns.emplace_back(table_function_column_description);
}
else
{
auto table_id = getContext()->resolveStorageID(table_expression.database_and_table_name);
getContext()->checkAccess(AccessType::SHOW_COLUMNS, table_id);
auto table = DatabaseCatalog::instance().getTable(table_id, getContext());
auto table_lock = table->lockForShare(getContext()->getInitialQueryId(), settings.lock_acquire_timeout);
auto metadata_snapshot = table->getInMemoryMetadataPtr();
storage_snapshot = table->getStorageSnapshot(metadata_snapshot, getContext());
auto metadata_column_descriptions = metadata_snapshot->getColumns();
for (const auto & metadata_column_description : metadata_column_descriptions)
columns.emplace_back(metadata_column_description);
}
bool extend_object_types = settings.describe_extend_object_types && storage_snapshot;
bool include_subcolumns = settings.describe_include_subcolumns;
Block sample_block = getSampleBlock(include_subcolumns);
MutableColumns res_columns = sample_block.cloneEmptyColumns();
for (const auto & column : columns)
{
res_columns[0]->insert(column.name);
if (extend_object_types)
res_columns[1]->insert(storage_snapshot->getConcreteType(column.name)->getName());
else
res_columns[1]->insert(column.type->getName());
if (column.default_desc.expression)
{
res_columns[2]->insert(toString(column.default_desc.kind));
res_columns[3]->insert(queryToString(column.default_desc.expression));
}
else
{
res_columns[2]->insertDefault();
res_columns[3]->insertDefault();
}
res_columns[4]->insert(column.comment);
if (column.codec)
res_columns[5]->insert(queryToString(column.codec->as<ASTFunction>()->arguments));
else
res_columns[5]->insertDefault();
if (column.ttl)
res_columns[6]->insert(queryToString(column.ttl));
else
res_columns[6]->insertDefault();
if (include_subcolumns)
res_columns[7]->insertDefault();
}
if (include_subcolumns)
{
for (const auto & column : columns)
{
auto type = extend_object_types ? storage_snapshot->getConcreteType(column.name) : column.type;
IDataType::forEachSubcolumn([&](const auto & path, const auto & name, const auto & data)
{
res_columns[0]->insert(Nested::concatenateName(column.name, name));
res_columns[1]->insert(data.type->getName());
/// It's not trivial to calculate default expression for subcolumn.
/// So, leave it empty.
res_columns[2]->insertDefault();
res_columns[3]->insertDefault();
res_columns[4]->insert(column.comment);
if (column.codec && ISerialization::isSpecialCompressionAllowed(path))
res_columns[5]->insert(queryToString(column.codec->as<ASTFunction>()->arguments));
else
res_columns[5]->insertDefault();
if (column.ttl)
res_columns[6]->insert(queryToString(column.ttl));
else
res_columns[6]->insertDefault();
res_columns[7]->insert(1u);
}, ISerialization::SubstreamData(type->getDefaultSerialization()).withType(type));
}
}
BlockIO res;
size_t num_rows = res_columns[0]->size();
auto source = std::make_shared<SourceFromSingleChunk>(sample_block, Chunk(std::move(res_columns), num_rows));
res.pipeline = QueryPipeline(std::move(source));
return res;
}
}
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