pqxx::placeholders< COUNTER > Class Template Reference

Generate parameter placeholders for use in an SQL statement. More...

Public Member Functions
	placeholders ()
constexpr zview	view () const &noexcept
	Read an ephemeral version of the current placeholder text.
std::string	get () const
	Read the current placeholder text, as a std::string.
void	next () &
	Move on to the next parameter.
COUNTER	count () const noexcept
	Return the current placeholder number. The initial placeholder is 1.

Static Public Attributes
static constexpr unsigned int	max_params
	Maximum number of parameters we support.

Detailed Description

template<typename COUNTER = unsigned int>
class pqxx::placeholders< COUNTER >

Generate parameter placeholders for use in an SQL statement.

When you want to pass parameters to a prepared statement or a parameterised statement, you insert placeholders into the SQL. During invocation, the database replaces those with the respective parameter values you passed.

The placeholders look like $1 (for the first parameter value), $2 (for the second), and so on. You can just write those directly in your statement. But for those rare cases where it becomes difficult to track which number a placeholder should have, you can use a placeholders object to count and generate them in order.

Constructor & Destructor Documentation

placeholders()

template<typename COUNTER = unsigned int>

pqxx::placeholders< COUNTER >::placeholders ( )

inline

Member Function Documentation

count()

template<typename COUNTER = unsigned int>

COUNTER pqxx::placeholders< COUNTER >::count ( ) const

inlinenoexcept

Return the current placeholder number. The initial placeholder is 1.

get()

template<typename COUNTER = unsigned int>

std::string pqxx::placeholders< COUNTER >::get ( ) const

inline

Read the current placeholder text, as a std::string.

This will be slightly slower than converting to a zview. With most C++ implementations however, until you get into ridiculous numbers of parameters, the string will benefit from the Short String Optimization, or SSO.

next()

template<typename COUNTER = unsigned int>

void pqxx::placeholders< COUNTER >::next ( ) &

inline

Move on to the next parameter.

view()

template<typename COUNTER = unsigned int>

zview pqxx::placeholders< COUNTER >::view ( ) const &

inlineconstexprnoexcept

Read an ephemeral version of the current placeholder text.

Warning

Changing the current placeholder number will overwrite this. Use the view immediately, or lose it.

Member Data Documentation

max_params

template<typename COUNTER = unsigned int>

unsigned int pqxx::placeholders< COUNTER >::max_params

inlinestaticconstexpr

Initial value:

{
    (std::numeric_limits<COUNTER>::max)()}

Maximum number of parameters we support.

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The documentation for this class was generated from the following file:

• /builddir/build/BUILD/libpqxx-7.10.5-build/libpqxx-7.10.5/redhat-linux-build/include/pqxx/params.hxx