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#include <Formats/ReadSchemaUtils.h>
#include <IO/ReadBufferFromString.h>
#include <Interpreters/Context.h>
#include <Interpreters/evaluateConstantExpression.h>
#include <Interpreters/parseColumnsListForTableFunction.h>
#include <Parsers/ASTLiteral.h>
#include <Processors/Executors/PullingPipelineExecutor.h>
#include <Processors/Formats/IInputFormat.h>
#include <Processors/Transforms/AddingDefaultsTransform.h>
#include <QueryPipeline/Pipe.h>
#include <QueryPipeline/QueryPipelineBuilder.h>
#include <Storages/StorageValues.h>
#include <Storages/checkAndGetLiteralArgument.h>
#include <TableFunctions/TableFunctionFormat.h>
#include <TableFunctions/TableFunctionFactory.h>
namespace DB
{
namespace ErrorCodes
{
extern const int LOGICAL_ERROR;
extern const int NUMBER_OF_ARGUMENTS_DOESNT_MATCH;
}
void TableFunctionFormat::parseArguments(const ASTPtr & ast_function, ContextPtr context)
{
ASTs & args_func = ast_function->children;
if (args_func.size() != 1)
throw Exception(ErrorCodes::LOGICAL_ERROR, "Table function '{}' must have arguments", getName());
ASTs & args = args_func.at(0)->children;
if (args.size() != 2 && args.size() != 3)
throw Exception(ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH, "Table function '{}' requires 2 or 3 arguments: format, [structure], data", getName());
for (auto & arg : args)
arg = evaluateConstantExpressionOrIdentifierAsLiteral(arg, context);
format = checkAndGetLiteralArgument<String>(args[0], "format");
data = checkAndGetLiteralArgument<String>(args.back(), "data");
if (args.size() == 3)
structure = checkAndGetLiteralArgument<String>(args[1], "structure");
}
ColumnsDescription TableFunctionFormat::getActualTableStructure(ContextPtr context, bool /*is_insert_query*/) const
{
if (structure == "auto")
{
SingleReadBufferIterator read_buffer_iterator(std::make_unique<ReadBufferFromString>(data));
return readSchemaFromFormat(format, std::nullopt, read_buffer_iterator, false, context);
}
return parseColumnsListFromString(structure, context);
}
Block TableFunctionFormat::parseData(ColumnsDescription columns, ContextPtr context) const
{
Block block;
for (const auto & name_and_type : columns.getAllPhysical())
block.insert({name_and_type.type->createColumn(), name_and_type.type, name_and_type.name});
auto read_buf = std::make_unique<ReadBufferFromString>(data);
auto input_format = context->getInputFormat(format, *read_buf, block, context->getSettingsRef().max_block_size);
QueryPipelineBuilder builder;
builder.init(Pipe(input_format));
if (columns.hasDefaults())
{
builder.addSimpleTransform([&](const Block & header)
{
return std::make_shared<AddingDefaultsTransform>(header, columns, *input_format, context);
});
}
auto pipeline = std::make_unique<QueryPipeline>(QueryPipelineBuilder::getPipeline(std::move(builder)));
auto reader = std::make_unique<PullingPipelineExecutor>(*pipeline);
std::vector<Block> blocks;
while (reader->pull(block))
blocks.push_back(std::move(block));
if (blocks.size() == 1)
return blocks[0];
/// In case when data contains more then 1 block we combine
/// them all to one big block (this is considered a rare case).
return concatenateBlocks(blocks);
}
StoragePtr TableFunctionFormat::executeImpl(const ASTPtr & /*ast_function*/, ContextPtr context, const std::string & table_name, ColumnsDescription /*cached_columns*/, bool is_insert_query) const
{
auto columns = getActualTableStructure(context, is_insert_query);
Block res_block = parseData(columns, context);
auto res = std::make_shared<StorageValues>(StorageID(getDatabaseName(), table_name), columns, res_block);
res->startup();
return res;
}
static const FunctionDocumentation format_table_function_documentation =
{
.description=R"(
Extracts table structure from data and parses it according to specified input format.
Syntax: `format(format_name, data)`.
Parameters:
- `format_name` - the format of the data.
- `data ` - String literal or constant expression that returns a string containing data in specified format.
Returned value: A table with data parsed from `data` argument according specified format and extracted schema.
)",
.examples
{
{
"First example",
R"(
Query:
```
:) select * from format(JSONEachRow,
$$
{"a": "Hello", "b": 111}
{"a": "World", "b": 123}
{"a": "Hello", "b": 112}
{"a": "World", "b": 124}
$$)
```
Result:
```
┌───b─┬─a─────┐
│ 111 │ Hello │
│ 123 │ World │
│ 112 │ Hello │
│ 124 │ World │
└─────┴───────┘
```
)", ""
},
{
"Second example",
R"(
Query:
```
:) desc format(JSONEachRow,
$$
{"a": "Hello", "b": 111}
{"a": "World", "b": 123}
{"a": "Hello", "b": 112}
{"a": "World", "b": 124}
$$)
```
Result:
```
┌─name─┬─type──────────────┬─default_type─┬─default_expression─┬─comment─┬─codec_expression─┬─ttl_expression─┐
│ b │ Nullable(Float64) │ │ │ │ │ │
│ a │ Nullable(String) │ │ │ │ │ │
└──────┴───────────────────┴──────────────┴────────────────────┴─────────┴──────────────────┴────────────────┘
```
)", ""
},
},
.categories{"format", "table-functions"}
};
void registerTableFunctionFormat(TableFunctionFactory & factory)
{
factory.registerFunction<TableFunctionFormat>({format_table_function_documentation, false}, TableFunctionFactory::CaseInsensitive);
}
}
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