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77 lines
2.7 KiB
C++
77 lines
2.7 KiB
C++
/* Definition of the pqxx::nontransaction class.
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*
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* pqxx::nontransaction provides nontransactional database access
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*
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* DO NOT INCLUDE THIS FILE DIRECTLY; include pqxx/nontransaction instead.
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*
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* Copyright (c) 2000-2022, Jeroen T. Vermeulen.
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*
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* See COPYING for copyright license. If you did not receive a file called
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* COPYING with this source code, please notify the distributor of this
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* mistake, or contact the author.
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*/
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#ifndef PQXX_H_NONTRANSACTION
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#define PQXX_H_NONTRANSACTION
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#if !defined(PQXX_HEADER_PRE)
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# error "Include libpqxx headers as <pqxx/header>, not <pqxx/header.hxx>."
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#endif
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#include "pqxx/connection.hxx"
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#include "pqxx/result.hxx"
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#include "pqxx/transaction.hxx"
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namespace pqxx
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{
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using namespace std::literals;
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/// Simple "transaction" class offering no transactional integrity.
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/**
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* @ingroup transactions
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*
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* nontransaction, like transaction or any other transaction_base-derived
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* class, provides access to a database through a connection. Unlike its
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* siblings, however, nontransaction does not maintain any kind of
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* transactional integrity. This may be useful eg. for read-only access to the
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* database that does not require a consistent, atomic view on its data; or for
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* operations that are not allowed within a backend transaction, such as
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* creating tables.
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*
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* For queries that update the database, however, a real transaction is likely
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* to be faster unless the transaction consists of only a single record update.
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*
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* Also, you can keep a nontransaction open for as long as you like. Actual
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* back-end transactions are limited in lifespan, and will sometimes fail just
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* because they took too long to execute or were left idle for too long. This
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* will not happen with a nontransaction (although the connection may still
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* time out, e.g. when the network is unavailable for a very long time).
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*
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* Any query executed in a nontransaction is committed immediately, and neither
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* commit() nor abort() has any effect.
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*
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* Database features that require a backend transaction, such as cursors or
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* large objects, will not work in a nontransaction.
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*/
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class PQXX_LIBEXPORT nontransaction final : public transaction_base
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{
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public:
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/// Constructor.
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/** Create a "dummy" transaction.
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* @param c Connection in which this "transaction" will operate.
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* @param tname Optional tname for the transaction, beginning with a letter
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* and containing only letters and digits.
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*/
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nontransaction(connection &c, std::string_view tname = ""sv) :
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transaction_base{c, tname, std::shared_ptr<std::string>{}}
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{
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register_transaction();
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}
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virtual ~nontransaction() override { close(); }
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private:
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virtual void do_commit() override {}
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};
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} // namespace pqxx
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#endif
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