ClickHouse/dbms/src/Formats/ValuesBlockInputStream.cpp

#include <IO/ReadHelpers.h>
#include <Interpreters/evaluateConstantExpression.h>
#include <Interpreters/Context.h>
#include <Interpreters/convertFieldToType.h>
#include <Parsers/TokenIterator.h>
#include <Parsers/ExpressionListParsers.h>
#include <Formats/ValuesBlockInputStream.h>
#include <Formats/FormatFactory.h>
#include <Formats/BlockInputStreamFromRowInputStream.h>
#include <Common/FieldVisitors.h>
#include <Core/Block.h>
#include <Common/typeid_cast.h>


namespace DB
{

namespace ErrorCodes
{
    extern const int CANNOT_PARSE_INPUT_ASSERTION_FAILED;
    extern const int CANNOT_PARSE_QUOTED_STRING;
    extern const int CANNOT_PARSE_NUMBER;
    extern const int CANNOT_PARSE_DATE;
    extern const int CANNOT_PARSE_DATETIME;
    extern const int CANNOT_READ_ARRAY_FROM_TEXT;
    extern const int CANNOT_PARSE_DATE;
    extern const int SYNTAX_ERROR;
    extern const int VALUE_IS_OUT_OF_RANGE_OF_DATA_TYPE;
    extern const int CANNOT_CREATE_EXPRESSION_TEMPLATE;
    extern const int CANNOT_PARSE_EXPRESSION_USING_TEMPLATE;
    extern const int CANNOT_EVALUATE_EXPRESSION_TEMPLATE;
}


ValuesBlockInputStream::ValuesBlockInputStream(ReadBuffer & istr_, const Block & header_, const Context & context_,
                                               const FormatSettings & format_settings, UInt64 max_block_size_)
        : istr(istr_), header(header_), context(std::make_unique<Context>(context_)),
          format_settings(format_settings), max_block_size(max_block_size_)
{
    templates.resize(header.columns());
    /// In this format, BOM at beginning of stream cannot be confused with value, so it is safe to skip it.
    skipBOMIfExists(istr);
}


bool ValuesBlockInputStream::read(MutableColumns & columns)
{
    size_t num_columns = columns.size();

    skipWhitespaceIfAny(istr);

    if (istr.eof() || *istr.position() == ';')
        return false;

    /** Typically, this is the usual format for streaming parsing.
      * But as an exception, it also supports processing arbitrary expressions instead of values.
      * This is very inefficient. But if there are no expressions, then there is no overhead.
      */

    assertChar('(', istr);

    for (size_t i = 0; i < num_columns; ++i)
    {
        skipWhitespaceIfAny(istr);
        istr.setCheckpoint();

        bool rollback_on_exception = false;
        try
        {
            if (templates[i])
            {
                templates[i].value().parseExpression(istr, format_settings);
            }
            else
            {
                header.getByPosition(i).type->deserializeAsTextQuoted(*columns[i], istr, format_settings);
                rollback_on_exception = true;
            }

            skipWhitespaceIfAny(istr);

            if (i != num_columns - 1)
                assertChar(',', istr);
            else
                assertChar(')', istr);
        }
        catch (const Exception & e)
        {
            if (!format_settings.values.interpret_expressions)
                throw;

            /** The normal streaming parser could not parse the value.
              * Let's try to parse it with a SQL parser as a constant expression.
              * This is an exceptional case.
              */
            if (e.code() == ErrorCodes::CANNOT_PARSE_INPUT_ASSERTION_FAILED
                || e.code() == ErrorCodes::CANNOT_PARSE_QUOTED_STRING
                || e.code() == ErrorCodes::CANNOT_PARSE_NUMBER
                || e.code() == ErrorCodes::CANNOT_PARSE_DATE
                || e.code() == ErrorCodes::CANNOT_PARSE_DATETIME
                || e.code() == ErrorCodes::CANNOT_READ_ARRAY_FROM_TEXT
                || e.code() == ErrorCodes::CANNOT_PARSE_EXPRESSION_USING_TEMPLATE)
            {
                if (rollback_on_exception)
                    columns[i]->popBack(1);

                // TODO read(MutableColumns & columns) should not know number of rows in block an should not assign to columns
                if (likely(rows_in_block))
                {
                    if (e.code() == ErrorCodes::CANNOT_PARSE_EXPRESSION_USING_TEMPLATE)
                    {
                        /// Expression in the current row is not match generated on the first row template.
                        /// Evaluate expressions, which were parsed using this template.
                        columns[i] = std::move(*templates[i].value().evaluateAll()).mutate();
                        /// And do not use the template anymore.
                        templates[i].reset();
                    }
                    else if (templates[i])
                        throw;
                }

                istr.rollbackToCheckpoint();
                parseExpression(columns, i, rows_in_block == 0);

                skipWhitespaceIfAny(istr);

                if (i != num_columns - 1)
                    assertChar(',', istr);
                else
                    assertChar(')', istr);
            }
            else
                throw;
        }

        istr.dropCheckpoint();
    }

    skipWhitespaceIfAny(istr);
    if (!istr.eof() && *istr.position() == ',')
        ++istr.position();

    return true;
}

Block ValuesBlockInputStream::readImpl()
{
    MutableColumns columns = header.cloneEmptyColumns();

    for (rows_in_block = 0; rows_in_block < max_block_size; ++rows_in_block)
    {
        try
        {
            if (!read(columns))
                break;
            ++total_rows;
        }
        catch (Exception & e)
        {
            if (isParseError(e.code()))
                e.addMessage(" at row " + std::to_string(total_rows));
            throw;
        }
    }

    /// Evaluate expressions, which were parsed using this template, if any
    for (size_t i = 0; i < columns.size(); ++i)
    {
        if (templates[i])
        {
            columns[i] = std::move(*templates[i].value().evaluateAll()).mutate();
            templates[i].reset();
        }
    }

    if (columns.empty() || columns[0]->empty())
        return {};

    return header.cloneWithColumns(std::move(columns));
}

Field
ValuesBlockInputStream::parseExpression(MutableColumns & columns, size_t column_idx, bool generate_template)
{
    const IDataType & type = *header.getByPosition(column_idx).type;

    Expected expected;

    // TODO make tokenizer to work with buffers, not only with continuous memory
    Tokens tokens(istr.position(), istr.buffer().end());
    TokenIterator token_iterator(tokens);

    ASTPtr ast;
    if (!parser.parse(token_iterator, ast, expected))
    {
        istr.rollbackToCheckpoint();
        throw Exception("Cannot parse expression of type " + type.getName() + " here: "
                        + String(istr.position(), std::min(SHOW_CHARS_ON_SYNTAX_ERROR, istr.buffer().end() - istr.position())),
                        ErrorCodes::SYNTAX_ERROR);
    }

    std::pair<Field, DataTypePtr> value_raw = evaluateConstantExpression(ast, *context);
    Field value = convertFieldToType(value_raw.first, type, value_raw.second.get());

    /// Check that we are indeed allowed to insert a NULL.
    if (value.isNull() && !type.isNullable())
    {
        istr.rollbackToCheckpoint();
        throw Exception{"Expression returns value " + applyVisitor(FieldVisitorToString(), value)
                        + ", that is out of range of type " + type.getName()
                        + ", at: " +
                        String(istr.position(), std::min(SHOW_CHARS_ON_SYNTAX_ERROR, istr.buffer().end() - istr.position())),
                        ErrorCodes::VALUE_IS_OUT_OF_RANGE_OF_DATA_TYPE};
    }

    istr.position() = const_cast<char *>(token_iterator->begin);

    if (generate_template)
    {
        try
        {
            templates[column_idx] = ConstantExpressionTemplate(type, TokenIterator(tokens), token_iterator, *context);
            istr.rollbackToCheckpoint();
            templates[column_idx].value().parseExpression(istr, format_settings);
        }
        catch (DB::Exception &)
        {
            /// Continue parsing without template
            templates[column_idx].reset();
            columns[column_idx]->insert(value);
            istr.position() = const_cast<char *>(token_iterator->begin);
        }
    }
    else
    {
        columns[column_idx]->insert(value);
    }
    return value;
}


void registerInputFormatValues(FormatFactory & factory)
{
    factory.registerInputFormat("Values", [](
        ReadBuffer & buf,
        const Block & sample,
        const Context & context,
        UInt64 max_block_size,
        const FormatSettings & settings)
    {
        return std::make_shared<ValuesBlockInputStream>(buf, sample, context, settings, max_block_size);
    });
}

}