pqxx::subtransaction Class Reference
"Transaction" nested within another transaction More...
#include <subtransaction.hxx>
Inheritance diagram for pqxx::subtransaction:
Public Member Functions | |
| subtransaction (dbtransaction &t, std::string_view tname=""sv) | |
| Nest a subtransaction nested in another transaction. More... | |
| subtransaction (subtransaction &t, std::string_view name=""sv) | |
| Nest a subtransaction in another subtransaction. More... | |
| virtual | ~subtransaction () noexcept override |
 Public Member Functions inherited from pqxx::transaction_base | |
| transaction_base ()=delete | |
| transaction_base (transaction_base const &)=delete | |
| transaction_base (transaction_base &&)=delete | |
| transaction_base & | operator= (transaction_base const &)=delete |
| transaction_base & | operator= (transaction_base &&)=delete |
| virtual | ~transaction_base ()=0 |
| void | commit () |
| Commit the transaction. More... | |
| void | abort () |
| Abort the transaction. More... | |
| connection & | conn () const |
| The connection in which this transaction lives. More... | |
| void | set_variable (std::string_view var, std::string_view value) |
| Set session variable using SQL "SET" command. More... | |
| std::string | get_variable (std::string_view) |
| Read session variable using SQL "SHOW" command. More... | |
| std::string_view | name () const noexcept |
| Transaction name, if you passed one to the constructor; or empty string. More... | |
| template<> | |
| zview | query_value (zview query, std::string_view desc)=delete |
| Forbidden specialisation: underlying buffer immediately goes out of scope. More... | |
| std::string | esc (char const text[]) const |
| Escape string for use as SQL string literal in this transaction. More... | |
| std::string | esc (char const text[], std::size_t maxlen) const |
| Escape string for use as SQL string literal in this transaction. More... | |
| std::string | esc (std::string_view text) const |
| Escape string for use as SQL string literal in this transaction. More... | |
| std::string | esc_raw (unsigned char const data[], std::size_t len) const |
| Escape binary data for use as SQL string literal in this transaction. More... | |
| std::string | esc_raw (zview) const |
| Escape binary data for use as SQL string literal in this transaction. More... | |
| std::string | unesc_raw (zview text) const |
| Unescape binary data, e.g. from a table field or notification payload. More... | |
| std::string | unesc_raw (char const *text) const |
| Unescape binary data, e.g. from a table field or notification payload. More... | |
| template<typename T > | |
| std::string | quote (T const &t) const |
| Represent object as SQL string, including quoting & escaping. More... | |
| std::string | quote_raw (unsigned char const bin[], std::size_t len) const |
| Binary-escape and quote a binary string for use as an SQL constant. More... | |
| std::string | quote_raw (zview bin) const |
| Binary-escape and quote a binary string for use as an SQL constant. More... | |
| std::string | quote_name (std::string_view identifier) const |
| Escape an SQL identifier for use in a query. More... | |
| std::string | esc_like (std::string_view bin, char escape_char='\\') const |
| Escape string for literal LIKE match. More... | |
| result | exec (std::string_view query, std::string_view desc=std::string_view{}) |
| Execute a command. More... | |
| result | exec (std::stringstream const &query, std::string_view desc=std::string_view{}) |
| Execute a command. More... | |
| result | exec0 (zview query, std::string_view desc=std::string_view{}) |
| Execute command, which should return zero rows of data. More... | |
| row | exec1 (zview query, std::string_view desc=std::string_view{}) |
| Execute command returning a single row of data. More... | |
| result | exec_n (result::size_type rows, zview query, std::string_view desc=std::string_view{}) |
| Execute command, expect given number of rows. More... | |
| template<typename TYPE > | |
| TYPE | query_value (zview query, std::string_view desc=std::string_view{}) |
| Perform query, expecting exactly 1 row with 1 field, and convert it. More... | |
| template<typename... TYPE> | |
| auto | stream (std::string_view query) |
| Execute a query, and loop over the results row by row. More... | |
| template<typename... Args> | |
| result | exec_params (zview query, Args &&...args) |
| Execute an SQL statement with parameters. More... | |
| template<typename... Args> | |
| row | exec_params1 (zview query, Args &&...args) |
| template<typename... Args> | |
| result | exec_params0 (zview query, Args &&...args) |
| template<typename... Args> | |
| result | exec_params_n (std::size_t rows, zview query, Args &&...args) |
| template<typename... Args> | |
| result | exec_prepared (zview statement, Args &&...args) |
| Execute a prepared statement, with optional arguments. More... | |
| template<typename... Args> | |
| row | exec_prepared1 (zview statement, Args &&...args) |
| Execute a prepared statement, and expect a single-row result. More... | |
| template<typename... Args> | |
| result | exec_prepared0 (zview statement, Args &&...args) |
| Execute a prepared statement, and expect a result with zero rows. More... | |
| template<typename... Args> | |
| result | exec_prepared_n (result::size_type rows, zview statement, Args &&...args) |
| Execute a prepared statement, expect a result with given number of rows. More... | |
| void | process_notice (char const msg[]) const |
| Have connection process a warning message. More... | |
| void | process_notice (zview msg) const |
| Have connection process a warning message. More... | |
Additional Inherited Members | |
| Protected Member Functions inherited from pqxx::dbtransaction | |
| dbtransaction (connection &c) | |
| Begin transaction. More... | |
| dbtransaction (connection &c, std::string_view tname) | |
| Begin transaction. More... | |
| dbtransaction (connection &c, std::string_view tname, std::shared_ptr< std::string > rollback_cmd) | |
| Begin transaction. More... | |
| Protected Member Functions inherited from pqxx::transaction_base | |
| transaction_base (connection &c, std::string_view tname, std::shared_ptr< std::string > rollback_cmd) | |
| Create a transaction (to be called by implementation classes only). More... | |
| transaction_base (connection &c, std::string_view tname) | |
| Create a transaction (to be called by implementation classes only). More... | |
| transaction_base (connection &c) | |
| Create a transaction (to be called by implementation classes only). More... | |
| void | register_transaction () |
| Register this transaction with the connection. More... | |
| void | close () noexcept |
| End transaction. To be called by implementing class' destructor. More... | |
| virtual void | do_abort () |
| Transaction type-specific way of aborting a transaction. More... | |
| void | set_rollback_cmd (std::shared_ptr< std::string > cmd) |
| Set the rollback command. More... | |
| result | direct_exec (std::string_view, std::string_view desc=""sv) |
| Execute query on connection directly. More... | |
| result | direct_exec (std::shared_ptr< std::string >, std::string_view desc=""sv) |
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 &C)
{
string const temptable = "fleetingtable";
work W(C, "do_job");
do_firstpart(W);
// Attempt to delete our temporary table if it already existed.
try
{
subtransaction S(W, "droptemp");
S.exec0("DROP TABLE " + temptable);
S.commit();
}
catch (undefined_table const &)
{
// 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.exec0("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.
- Warning
- While the subtransaction is "live," you cannot execute queries or open streams etc. on its parent transaction. A transaction can have at most one object of a type derived from
pqxx::internal::transactionfocusactive on it at a time.
Constructor & Destructor Documentation
◆ subtransaction() [1/2]
|
explicit |
Nest a subtransaction nested in another transaction.
References pqxx::connection::adorn_name(), pqxx::transaction_base::conn(), pqxx::transaction_base::direct_exec(), and pqxx::transaction_base::set_rollback_cmd().
◆ subtransaction() [2/2]
|
explicit |
Nest a subtransaction in another subtransaction.
◆ ~subtransaction()
|
overridevirtualnoexcept |
References pqxx::transaction_base::close(), and pqxx::transaction_base::direct_exec().
The documentation for this class was generated from the following files:
- subtransaction.hxx
- subtransaction.cxx
