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61 lines
2.8 KiB
C++
61 lines
2.8 KiB
C++
#pragma once
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#include <mysqlxx/Connection.h>
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#include <mysqlxx/Transaction.h>
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#include <mysqlxx/Pool.h>
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#include <common/LocalDate.h>
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#include <common/LocalDateTime.h>
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#include <mysqlxx/Null.h>
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/** 'mysqlxx' - very simple library for replacement of 'mysql++' library.
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*
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* For whatever reason, in Yandex.Metrica, back in 2008, 'mysql++' library was used.
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* There are the following shortcomings of 'mysql++':
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* 1. Too rich functionality: most of it is not used.
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* 2. Low performance (when used for Yandex.Metrica).
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*
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* Low performance is caused by the following reasons:
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*
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* 1. Excessive copying: 'mysqlpp::Row' works like 'std::vector<std::string>'.
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* Content of MYSQL_ROW is copied inside it.
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* But MYSQL_ROW is a 'char**', that is allocated in single piece,
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* where values are stored consecutively as (non-zero-terminated) strings.
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*
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* 2. Too slow methods for converting values to numbers.
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* In mysql++, it is done through std::stringstream.
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* This is slower than POSIX functions (strtoul, etc).
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* In turn, this is slower than simple hand-coded functions,
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* that doesn't respect locales and unused by MySQL number representations.
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*
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* 3. Too slow methods of escaping and quoting.
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* In mysql++, 'mysql_real_escape_string' is used, that works correct
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* even for charsets, that are not based on ASCII (examples: UTF-16, Shift-JIS).
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* But when using charsets based on ASCII, as UTF-8,
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* (in general, charsets, where escape characters are represented in same way as in ASCII,
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* and where that codes cannot appear in representation of another characters)
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* this function is redundant.
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*
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* 4. Too much garbage (dynamic_cast, typeid when converting values).
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*
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* Low performance cause the following effects:
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* 1. In sequential read from MySQL table, the client CPU becomes a bottleneck, while MySQL server is not loaded.
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* When using bare MySQL C API, this doesn't happen.
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* 2. Sequential read from MySQL is lower than 30MB/s.
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*
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* Warning!
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*
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* mysqlxx is implemented as very simple wrapper around MySQL C API,
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* and implements only limited subset of mysql++ interface, that we use.
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* And for the sake of simplicity, some functions work only with certain assumptions,
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* or with slightly different semantic than in mysql++.
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* And we don't care about cross-platform usage of mysqlxx.
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* These assumptions are specific for Yandex.Metrica. Your mileage may vary.
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*
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* mysqlxx could not be considered as separate full-featured library,
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* because it is developed from the principle - "everything that we don't need is not implemented",
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* and also the library depends on some other libraries from Yandex.Metrica code.
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* (dependencied could be easily removed if necessary).
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* It is assumed that the user will add all missing functionality that is needed.
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*/
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