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271 lines
8.1 KiB
C++
271 lines
8.1 KiB
C++
#include <IO/ReadHelpers.h>
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#include <Formats/JSONEachRowRowInputStream.h>
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#include <Formats/FormatFactory.h>
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#include <Formats/BlockInputStreamFromRowInputStream.h>
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#include <DataTypes/NestedUtils.h>
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namespace DB
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{
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namespace ErrorCodes
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{
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extern const int INCORRECT_DATA;
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extern const int CANNOT_READ_ALL_DATA;
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extern const int LOGICAL_ERROR;
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}
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namespace
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{
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enum
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{
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UNKNOWN_FIELD = size_t(-1),
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NESTED_FIELD = size_t(-2)
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};
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}
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JSONEachRowRowInputStream::JSONEachRowRowInputStream(ReadBuffer & istr_, const Block & header_, const FormatSettings & format_settings)
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: istr(istr_), header(header_), format_settings(format_settings), name_map(header.columns())
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{
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/// In this format, BOM at beginning of stream cannot be confused with value, so it is safe to skip it.
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skipBOMIfExists(istr);
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size_t num_columns = header.columns();
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for (size_t i = 0; i < num_columns; ++i)
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{
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const String & colname = columnName(i);
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name_map[colname] = i; /// NOTE You could place names more cache-locally.
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if (format_settings.import_nested_json)
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{
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const auto splitted = Nested::splitName(colname);
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if (!splitted.second.empty())
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{
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const StringRef table_name(colname.data(), splitted.first.size());
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name_map[table_name] = NESTED_FIELD;
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}
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}
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}
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prev_positions.assign(num_columns, name_map.end());
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}
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const String & JSONEachRowRowInputStream::columnName(size_t i) const
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{
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return header.getByPosition(i).name;
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}
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inline size_t JSONEachRowRowInputStream::columnIndex(const StringRef & name, size_t key_index)
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{
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/// Optimization by caching the order of fields (which is almost always the same)
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/// and a quick check to match the next expected field, instead of searching the hash table.
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if (prev_positions.size() > key_index
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&& prev_positions[key_index] != name_map.end()
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&& name == prev_positions[key_index]->first)
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{
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return prev_positions[key_index]->second;
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}
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else
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{
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const auto it = name_map.find(name);
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if (name_map.end() != it)
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{
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if (key_index < prev_positions.size())
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prev_positions[key_index] = it;
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return it->second;
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}
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else
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return UNKNOWN_FIELD;
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}
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}
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/** Read the field name and convert it to column name
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* (taking into account the current nested name prefix)
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* Resulting StringRef is valid only before next read from buf.
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*/
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StringRef JSONEachRowRowInputStream::readColumnName(ReadBuffer & buf)
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{
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// This is just an optimization: try to avoid copying the name into current_column_name
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if (nested_prefix_length == 0 && buf.position() + 1 < buf.buffer().end())
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{
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char * next_pos = find_first_symbols<'\\', '"'>(buf.position() + 1, buf.buffer().end());
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if (next_pos != buf.buffer().end() && *next_pos != '\\')
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{
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/// The most likely option is that there is no escape sequence in the key name, and the entire name is placed in the buffer.
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assertChar('"', buf);
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StringRef res(buf.position(), next_pos - buf.position());
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buf.position() = next_pos + 1;
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return res;
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}
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}
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current_column_name.resize(nested_prefix_length);
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readJSONStringInto(current_column_name, buf);
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return current_column_name;
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}
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static inline void skipColonDelimeter(ReadBuffer & istr)
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{
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skipWhitespaceIfAny(istr);
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assertChar(':', istr);
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skipWhitespaceIfAny(istr);
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}
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void JSONEachRowRowInputStream::skipUnknownField(const StringRef & name_ref)
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{
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if (!format_settings.skip_unknown_fields)
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throw Exception("Unknown field found while parsing JSONEachRow format: " + name_ref.toString(), ErrorCodes::INCORRECT_DATA);
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skipJSONField(istr, name_ref);
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}
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void JSONEachRowRowInputStream::readField(size_t index, MutableColumns & columns)
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{
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if (read_columns[index])
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throw Exception("Duplicate field found while parsing JSONEachRow format: " + columnName(index), ErrorCodes::INCORRECT_DATA);
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try
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{
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header.getByPosition(index).type->deserializeAsTextJSON(*columns[index], istr, format_settings);
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}
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catch (Exception & e)
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{
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e.addMessage("(while read the value of key " + columnName(index) + ")");
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throw;
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}
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read_columns[index] = true;
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}
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inline bool JSONEachRowRowInputStream::advanceToNextKey(size_t key_index)
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{
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skipWhitespaceIfAny(istr);
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if (istr.eof())
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throw Exception("Unexpected end of stream while parsing JSONEachRow format", ErrorCodes::CANNOT_READ_ALL_DATA);
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else if (*istr.position() == '}')
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{
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++istr.position();
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return false;
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}
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if (key_index > 0)
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{
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assertChar(',', istr);
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skipWhitespaceIfAny(istr);
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}
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return true;
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}
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void JSONEachRowRowInputStream::readJSONObject(MutableColumns & columns)
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{
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assertChar('{', istr);
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for (size_t key_index = 0; advanceToNextKey(key_index); ++key_index)
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{
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StringRef name_ref = readColumnName(istr);
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const size_t column_index = columnIndex(name_ref, key_index);
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if (unlikely(ssize_t(column_index) < 0))
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{
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/// name_ref may point directly to the input buffer
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/// and input buffer may be filled with new data on next read
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/// If we want to use name_ref after another reads from buffer, we must copy it to temporary string.
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current_column_name.assign(name_ref.data, name_ref.size);
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name_ref = StringRef(current_column_name);
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skipColonDelimeter(istr);
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if (column_index == UNKNOWN_FIELD)
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skipUnknownField(name_ref);
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else if (column_index == NESTED_FIELD)
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readNestedData(name_ref.toString(), columns);
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else
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throw Exception("Logical error: illegal value of column_index", ErrorCodes::LOGICAL_ERROR);
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}
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else
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{
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skipColonDelimeter(istr);
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readField(column_index, columns);
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}
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}
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}
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void JSONEachRowRowInputStream::readNestedData(const String & name, MutableColumns & columns)
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{
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current_column_name = name;
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current_column_name.push_back('.');
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nested_prefix_length = current_column_name.size();
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readJSONObject(columns);
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nested_prefix_length = 0;
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}
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bool JSONEachRowRowInputStream::read(MutableColumns & columns, RowReadExtension & ext)
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{
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skipWhitespaceIfAny(istr);
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/// We consume ;, or \n before scanning a new row, instead scanning to next row at the end.
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/// The reason is that if we want an exact number of rows read with LIMIT x
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/// from a streaming table engine with text data format, like File or Kafka
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/// then seeking to next ;, or \n would trigger reading of an extra row at the end.
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/// Semicolon is added for convenience as it could be used at end of INSERT query.
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if (!istr.eof() && (*istr.position() == ',' || *istr.position() == ';'))
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++istr.position();
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skipWhitespaceIfAny(istr);
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if (istr.eof())
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return false;
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size_t num_columns = columns.size();
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/// Set of columns for which the values were read. The rest will be filled with default values.
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read_columns.assign(num_columns, false);
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nested_prefix_length = 0;
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readJSONObject(columns);
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/// Fill non-visited columns with the default values.
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for (size_t i = 0; i < num_columns; ++i)
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if (!read_columns[i])
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header.getByPosition(i).type->insertDefaultInto(*columns[i]);
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/// return info about defaults set
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ext.read_columns = read_columns;
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return true;
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}
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void JSONEachRowRowInputStream::syncAfterError()
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{
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skipToUnescapedNextLineOrEOF(istr);
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}
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void registerInputFormatJSONEachRow(FormatFactory & factory)
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{
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factory.registerInputFormat("JSONEachRow", [](
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ReadBuffer & buf,
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const Block & sample,
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const Context &,
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UInt64 max_block_size,
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const FormatSettings & settings)
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{
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return std::make_shared<BlockInputStreamFromRowInputStream>(
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std::make_shared<JSONEachRowRowInputStream>(buf, sample, settings),
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sample, max_block_size, settings);
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});
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}
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}
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