pqxx::subtransaction Class Reference
"Transaction" nested within another transaction More...
#include <subtransaction.hxx>
Inheritance diagram for pqxx::subtransaction:
Public Member Functions | |
| subtransaction (dbtransaction &T, const std::string &Name=std::string()) | |
| Nest a subtransaction nested in another transaction. More... | |
| subtransaction (subtransaction &T, const std::string &Name=std::string()) | |
| Nest a subtransaction in another subtransaction. More... | |
| virtual | ~subtransaction () noexcept |
 Public Member Functions inherited from pqxx::internal::transactionfocus | |
| transactionfocus (transaction_base &t) | |
| transactionfocus ()=delete | |
| transactionfocus (const transactionfocus &)=delete | |
| transactionfocus & | operator= (const transactionfocus &)=delete |
| Public Member Functions inherited from pqxx::internal::namedclass | |
| namedclass (const std::string &Classname) | |
| namedclass (const std::string &Classname, const std::string &Name) | |
| const std::string & | name () const noexcept |
| Object name, or the empty string if no name was given. More... | |
| const std::string & | classname () const noexcept |
| Class name. More... | |
| std::string | description () const |
| Combination of class name and object name; or just class name. More... | |
| Public Member Functions inherited from pqxx::dbtransaction | |
| virtual | ~dbtransaction () |
| Public Member Functions inherited from pqxx::transaction_base | |
| transaction_base ()=delete | |
| transaction_base (const transaction_base &)=delete | |
| transaction_base & | operator= (const transaction_base &)=delete |
| virtual | ~transaction_base ()=0 |
| void | commit () |
| Commit the transaction. More... | |
| void | abort () |
| Abort the transaction. More... | |
| result | exec (const std::string &Query, const std::string &Desc=std::string()) |
| Execute query. More... | |
| result | exec (const std::stringstream &Query, const std::string &Desc=std::string()) |
| result | exec0 (const std::string &Query, const std::string &Desc=std::string()) |
| Execute query, which should zero rows of data. More... | |
| row | exec1 (const std::string &Query, const std::string &Desc=std::string()) |
| Execute query returning a single row of data. More... | |
| result | exec_n (size_t rows, const std::string &Query, const std::string &Desc=std::string()) |
| Execute query, expect given number of rows. More... | |
| connection_base & | conn () const |
| Connection this transaction is running in. More... | |
| void | set_variable (const std::string &Var, const std::string &Val) |
| Set session variable in this connection. More... | |
| std::string | get_variable (const std::string &) |
| Get currently applicable value of variable. More... | |
| std::string | esc (const char str[]) const |
| Escape string for use as SQL string literal in this transaction. More... | |
| std::string | esc (const char str[], size_t maxlen) const |
| Escape string for use as SQL string literal in this transaction. More... | |
| std::string | esc (const std::string &str) const |
| Escape string for use as SQL string literal in this transaction. More... | |
| std::string | esc_raw (const unsigned char data[], size_t len) const |
| Escape binary data for use as SQL string literal in this transaction. More... | |
| std::string | esc_raw (const std::string &) const |
| Escape binary data for use as SQL string literal in this transaction. More... | |
| std::string | unesc_raw (const std::string &text) const |
| Unescape binary data, e.g. from a table field or notification payload. More... | |
| std::string | unesc_raw (const char *text) const |
| Unescape binary data, e.g. from a table field or notification payload. More... | |
| template<typename T > | |
| std::string | quote (const T &t) const |
| Represent object as SQL string, including quoting & escaping. More... | |
| std::string | quote_raw (const unsigned char str[], size_t len) const |
| Binary-escape and quote a binarystring for use as an SQL constant. More... | |
| std::string | quote_raw (const std::string &str) const |
| std::string | quote_name (const std::string &identifier) const |
| Escape an SQL identifier for use in a query. More... | |
| template<typename ... Args> | |
| result | exec_params (const std::string &query, Args &&...args) |
| Execute an SQL statement with parameters. More... | |
| template<typename ... Args> | |
| row | exec_params1 (const std::string &query, Args &&... args) |
| template<typename ... Args> | |
| result | exec_params0 (const std::string &query, Args &&...args) |
| template<typename ... Args> | |
| result | exec_params_n (size_t rows, const std::string &query, Args &&...args) |
| internal::parameterized_invocation | parameterized (const std::string &query) |
| Parameterize a statement. More... | |
| template<typename ... Args> | |
| result | exec_prepared (const std::string &statement, Args &&... args) |
| Execute a prepared statement, with optional arguments. More... | |
| template<typename ... Args> | |
| row | exec_prepared1 (const std::string &statement, Args &&... args) |
| Execute a prepared statement, and expect a single-row result. More... | |
| template<typename ... Args> | |
| result | exec_prepared0 (const std::string &statement, Args &&... args) |
| Execute a prepared statement, and expect a result with zero rows. More... | |
| template<typename ... Args> | |
| result | exec_prepared_n (size_t rows, const std::string &statement, Args &&... args) |
| Execute a prepared statement, expect a result with given number of rows. More... | |
| prepare::invocation | prepared (const std::string &statement=std::string()) |
| Execute prepared statement. More... | |
| void | process_notice (const char Msg[]) const |
| Have connection process warning message. More... | |
| void | process_notice (const std::string &Msg) const |
| Have connection process warning message. More... | |
Additional Inherited Members | |
| Public Types inherited from pqxx::transaction_base | |
| using | isolation_tag = isolation_traits< read_committed > |
| If nothing else is known, our isolation level is at least read_committed. More... | |
| Protected Member Functions inherited from pqxx::internal::transactionfocus | |
| void | register_me () |
| void | unregister_me () noexcept |
| void | reg_pending_error (const std::string &) noexcept |
| bool | registered () const noexcept |
| Protected Member Functions inherited from pqxx::dbtransaction | |
| dbtransaction (connection_base &, const std::string &IsolationString, readwrite_policy rw=read_write) | |
| dbtransaction (connection_base &, bool direct=true, readwrite_policy rw=read_write) | |
| void | start_backend_transaction () |
| Start a transaction on the backend and set desired isolation level. More... | |
| virtual result | do_exec (const char Query[]) override |
| Sensible default implemented here: perform query. More... | |
| Protected Member Functions inherited from pqxx::transaction_base | |
| transaction_base (connection_base &c, bool direct=true) | |
| Create a transaction (to be called by implementation classes only) More... | |
| void | Begin () |
| Begin transaction (to be called by implementing class) More... | |
| void | End () noexcept |
| End transaction. To be called by implementing class' destructor. More... | |
| result | direct_exec (const char C[], int Retries=0) |
| Execute query on connection directly. More... | |
| void | reactivation_avoidance_clear () noexcept |
| Forget about any reactivation-blocking resources we tried to allocate. More... | |
| Static Protected Member Functions inherited from pqxx::dbtransaction | |
| static std::string | fullname (const std::string &ttype, const std::string &isolation) |
| Protected Attributes inherited from pqxx::internal::transactionfocus | |
| transaction_base & | m_trans |
| Protected Attributes inherited from pqxx::transaction_base | |
| internal::reactivation_avoidance_counter | m_reactivation_avoidance |
| Resources allocated in this transaction that make reactivation impossible. More... | |
Detailed Description
"Transaction" nested within another transaction
A subtransaction can be executed inside a backend transaction, or inside another subtransaction. This can be useful when, for example, statements in a transaction may harmlessly fail and you don't want them to abort the entire transaction. Here's an example of how a temporary table may be dropped before re-creating it, without failing if the table did not exist:
void do_job(connection_base &C)
{
const string temptable = "fleetingtable";
// Since we're dealing with a temporary table here, disallow automatic
// recovery of the connection in case it breaks.
C.inhibit_reactivation(true);
work W(C, "do_job");
do_firstpart(W);
// Attempt to delete our temporary table if it already existed
try
{
subtransaction S(W, "droptemp");
S.exec("DROP TABLE " + temptable);
S.commit();
}
catch (const undefined_table &)
{
// Table did not exist. Which is what we were hoping to achieve anyway.
// Carry on without regrets.
}
// S may have gone into a failed state and been destroyed, but the
// upper-level transaction W is still fine. We can continue to use it.
W.exec("CREATE TEMP TABLE " + temptable + "(bar integer, splat varchar)");
do_lastpart(W);
}
(This is just an example. If you really wanted to do drop a table without an error if it doesn't exist, you'd use DROP TABLE IF EXISTS.)
There are no isolation levels inside a transaction. They are not needed because all actions within the same backend transaction are always performed sequentially anyway.
Constructor & Destructor Documentation
◆ subtransaction() [1/2]
|
explicit |
Nest a subtransaction nested in another transaction.
◆ subtransaction() [2/2]
|
explicit |
Nest a subtransaction in another subtransaction.
References pqxx::internal::reactivation_avoidance_counter::clear(), pqxx::transaction_base::direct_exec(), pqxx::internal::reactivation_avoidance_counter::get(), pqxx::transaction_base::m_reactivation_avoidance, and pqxx::internal::namedclass::name().
◆ ~subtransaction()
|
virtualnoexcept |
The documentation for this class was generated from the following files:
- subtransaction.hxx
- subtransaction.cxx
