libpqxx 7.8.1
pqxx Namespace Reference

The home of all libpqxx classes, functions, templates, etc. More...

Namespaces

namespace  internal
 Internal items for libpqxx' own use. Do not use these yourself.
 
namespace  prepare
 

Classes

struct  argument_error
 Invalid argument passed to libpqxx, similar to std::invalid_argument. More...
 
class  array
 An SQL array received from the database. More...
 
class  array_parser
 Low-level array parser. More...
 
class  basic_fieldstream
 Input stream that gets its data from a result field. More...
 
class  basic_ilostream
 Input stream that gets its data from a large object. More...
 
class  basic_lostream
 Stream that reads and writes a large object. More...
 
class  basic_olostream
 Output stream that writes data back to a large object. More...
 
class  binarystring
 Binary data corresponding to PostgreSQL's "BYTEA" binary-string type. More...
 
class  blob
 
struct  broken_connection
 Exception class for lost or failed backend connection. More...
 
struct  check_violation
 
class  connecting
 An ongoing, non-blocking stepping stone to a connection. More...
 
class  connection
 Connection to a database. More...
 
class  const_reverse_row_iterator
 Reverse iterator for a row. Use as row::const_reverse_iterator. More...
 
class  const_row_iterator
 Iterator for fields in a row. Use as row::const_iterator. More...
 
struct  conversion_error
 Value conversion failed, e.g. when converting "Hello" to int. More...
 
struct  conversion_overrun
 Could not convert value to string: not enough buffer space. More...
 
class  cursor_base
 Common definitions for cursor types. More...
 
struct  data_exception
 Error in data provided to SQL statement. More...
 
class  dbtransaction
 Abstract transaction base class: bracket transactions on the database. More...
 
struct  deadlock_detected
 The ongoing transaction has deadlocked. Retrying it may help. More...
 
struct  disk_full
 
class  errorhandler
 Base class for error-handler callbacks. More...
 
class  exclusive_bound
 An exclusive boundary value to a pqxx::range. More...
 
struct  failure
 Run-time failure encountered by libpqxx, similar to std::runtime_error. More...
 
struct  feature_not_supported
 Database feature not supported in current setup. More...
 
class  field
 Reference to a field in a result set. More...
 
class  field_streambuf
 
struct  forbidden_conversion
 String traits for a forbidden type conversion. More...
 
struct  foreign_key_violation
 
struct  from_query_t
 Marker for stream_from constructors: "stream from query.". More...
 
struct  from_table_t
 Marker for stream_from constructors: "stream from table.". More...
 
struct  in_doubt_error
 "Help, I don't know whether transaction was committed successfully!" More...
 
class  inclusive_bound
 An inclusive boundary value to a pqxx::range. More...
 
struct  insufficient_privilege
 
struct  insufficient_resources
 Resource shortage on the server. More...
 
struct  integrity_constraint_violation
 
struct  internal_error
 Internal error in libpqxx library. More...
 
struct  invalid_cursor_name
 
struct  invalid_cursor_state
 
struct  invalid_sql_statement_name
 
class  largeobject
 Identity of a large object. More...
 
class  largeobject_streambuf
 Streambuf to use large objects in standard I/O streams. More...
 
class  largeobjectaccess
 Accessor for large object's contents. More...
 
struct  no_bound
 An unlimited boundary value to a pqxx::range. More...
 
struct  no_null
 Nullness traits describing a type which does not have a null value. More...
 
class  nontransaction
 Simple "transaction" class offering no transactional integrity. More...
 
struct  not_null_violation
 
class  notification_receiver
 
struct  nullness
 Traits describing a type's "null value," if any. More...
 
struct  nullness< binarystring >
 
struct  nullness< ENUM, std::enable_if_t< std::is_enum_v< ENUM > > >
 Nullness: Enums do not have an inherent null value. More...
 
struct  nullness< range< TYPE > >
 A range type does not have an innate null value. More...
 
struct  out_of_memory
 
class  params
 Build a parameter list for a parameterised or prepared statement. More...
 
class  pipeline
 Processes several queries in FIFO manner, optimized for high throughput. More...
 
class  placeholders
 Generate parameter placeholders for use in an SQL statement. More...
 
struct  plpgsql_error
 PL/pgSQL error. More...
 
struct  plpgsql_no_data_found
 
struct  plpgsql_raise
 Exception raised in PL/pgSQL procedure. More...
 
struct  plpgsql_too_many_rows
 
struct  protocol_violation
 Exception class for micommunication with the server. More...
 
class  quiet_errorhandler
 An error handler that suppresses any previously registered error handlers. More...
 
class  range
 A C++ equivalent to PostgreSQL's range types. More...
 
class  range_bound
 A range boundary value. More...
 
struct  range_error
 Something is out of range, similar to std::out_of_range. More...
 
struct  restrict_violation
 
class  result
 Result set containing data returned by a query or command. More...
 
class  row
 Reference to one row in a result. More...
 
struct  serialization_failure
 Transaction failed to serialize. Please retry it. More...
 
class  sql_error
 Exception class for failed queries. More...
 
class  stateless_cursor
 "Stateless cursor" class: easy API for retrieving parts of result sets More...
 
struct  statement_completion_unknown
 We can't tell whether our last statement succeeded. More...
 
class  stream_from
 Stream data from the database. More...
 
class  stream_to
 Efficiently write data directly to a database table. More...
 
struct  string_traits
 Traits class for use in string conversions. More...
 
struct  string_traits< binarystring >
 String conversion traits for binarystring. More...
 
struct  string_traits< char >
 You cannot convert a char to/from SQL. More...
 
struct  string_traits< range< TYPE > >
 String conversions for a range type. More...
 
struct  string_traits< signed char >
 You cannot convert a signed char to/from SQL. More...
 
struct  string_traits< std::byte >
 You cannot convert a std::byte to/from SQL. More...
 
struct  string_traits< unsigned char >
 You cannot convert an unsigned char to/from SQL. More...
 
class  subtransaction
 "Transaction" nested within another transaction More...
 
struct  syntax_error
 
struct  thread_safety_model
 Descriptor of library's thread-safety model. More...
 
struct  too_many_connections
 
class  transaction_base
 Interface definition (and common code) for "transaction" classes. More...
 
class  transaction_focus
 Base class for things that monopolise a transaction's attention. More...
 
struct  transaction_rollback
 The backend saw itself forced to roll back the ongoing transaction. More...
 
struct  undefined_column
 
struct  undefined_function
 
struct  undefined_table
 
struct  unexpected_null
 Could not convert null value: target type does not support null. More...
 
struct  unexpected_rows
 Query returned an unexpected number of rows. More...
 
struct  unique_violation
 
struct  usage_error
 Error in usage of libpqxx library, similar to std::logic_error. More...
 
struct  variable_set_to_null
 The caller attempted to set a variable to null, which is not allowed. More...
 
class  zview
 Marker-type wrapper: zero-terminated std::string_view. More...
 

Typedefs

using table_path = std::initializer_list< std::string_view >
 Representation of a PostgreSQL table path.
 
using connection_base = connection
 
using fieldstream = basic_fieldstream< char >
 
using ilostream = basic_ilostream< char >
 
using olostream = basic_olostream< char >
 
using lostream = basic_lostream< char >
 
using result_size_type = int
 Number of rows in a result set.
 
using result_difference_type = int
 Difference between result sizes.
 
using row_size_type = int
 Number of fields in a row of database data.
 
using row_difference_type = int
 Difference between row sizes.
 
using field_size_type = std::size_t
 Number of bytes in a field of database data.
 
using large_object_size_type = int64_t
 Number of bytes in a large object.
 
template<typename TYPE >
using strip_t = std::remove_cv_t< std::remove_reference_t< TYPE > >
 Remove any constness, volatile, and reference-ness from a type.
 
template<typename CONTAINER >
using value_type = strip_t< decltype(*std::begin(std::declval< CONTAINER >()))>
 The type of a container's elements.
 

Enumerations

enum  skip_init : int { nothing , openssl , crypto }
 Flags for skipping initialisation of SSL-related libraries. More...
 
enum class  error_verbosity : int { terse = 0 , normal = 1 , verbose = 2 }
 Error verbosity levels. More...
 
enum class  write_policy { read_only , read_write }
 Should a transaction be read-only, or read-write? More...
 
enum  isolation_level { read_committed , repeatable_read , serializable }
 Transaction isolation levels. More...
 
enum class  format : int { text = 0 , binary = 1 }
 Format code: is data text or binary? More...
 

Functions

template<typename... T>
void parse_composite (pqxx::internal::encoding_group enc, std::string_view text, T &...fields)
 Parse a string representation of a value of a composite type.
 
template<typename... T>
void parse_composite (std::string_view text, T &...fields)
 Parse a string representation of a value of a composite type.
 
template<typename... T>
std::size_t composite_size_buffer (T const &...fields) noexcept
 Estimate the buffer size needed to represent a value of a composite type.
 
template<typename... T>
char * composite_into_buf (char *begin, char *end, T const &...fields)
 Render a series of values as a single composite SQL value.
 
template<skip_init... SKIP>
void skip_init_ssl () noexcept
 Control initialisation of OpenSSL and libcrypto libraries.
 
std::string encrypt_password (char const user[], char const password[])
 Encrypt a password.
 
std::string encrypt_password (zview user, zview password)
 Encrypt password.
 
template<>
bool field::to< std::string > (std::string &obj) const
 
template<>
bool field::to< std::string > (std::string &obj, std::string const &default_value) const
 
template<>
bool field::to< std::string_view > (std::string_view &obj) const
 
template<>
bool field::to< std::string_view > (std::string_view &obj, std::string_view const &default_value) const
 
template<>
std::string_view field::as< std::string_view > () const
 
template<>
std::string_view field::as< std::string_view > (std::string_view const &default_value) const
 
template<typename CHAR >
std::basic_ostream< CHAR > & operator<< (std::basic_ostream< CHAR > &s, field const &value)
 Write a result field to any type of stream.
 
template<typename T >
from_string (field const &value)
 Convert a field's value to type T.
 
template<>
std::nullptr_t from_string< std::nullptr_t > (field const &value)
 Convert a field's value to nullptr_t.
 
template<>
std::string to_string (field const &value)
 Convert a field to a string.
 
const_row_iterator operator+ (const_row_iterator::difference_type o, const_row_iterator const &i) noexcept
 
template<typename ITER , typename ACCESS >
std::string separated_list (std::string_view sep, ITER begin, ITER end, ACCESS access)
 Represent sequence of values as a string, joined by a given separator.
 
template<typename ITER >
std::string separated_list (std::string_view sep, ITER begin, ITER end)
 Render sequence as a string, using given separator between items.
 
template<typename CONTAINER >
auto separated_list (std::string_view sep, CONTAINER const &c) -> typename std::enable_if<(not std::is_void< decltype(std::begin(c))>::value and not std::is_void< decltype(std::end(c))>::value), std::string >::type
 Render items in a container as a string, using given separator.
 
template<typename TUPLE , std::size_t INDEX = 0, typename ACCESS , typename std::enable_if<(INDEX==std::tuple_size< TUPLE >::value - 1), int >::type = 0>
std::string separated_list (std::string_view, TUPLE const &t, ACCESS const &access)
 Render items in a tuple as a string, using given separator.
 
template<typename TUPLE , std::size_t INDEX = 0, typename std::enable_if<(INDEX<=std::tuple_size< TUPLE >::value), int >::type = 0>
std::string separated_list (std::string_view sep, TUPLE const &t)
 
template<typename TYPE >
void oops_forbidden_conversion () noexcept
 Nonexistent function to indicate a disallowed type conversion.
 
template<>
std::string_view transaction_base::query_value< std::string_view > (zview query, std::string_view desc)=delete
 Forbidden specialisation: underlying buffer immediately goes out of scope.
 
template<typename TRANSACTION_CALLBACK >
auto perform (TRANSACTION_CALLBACK &&callback, int attempts=3) -> std::invoke_result_t< TRANSACTION_CALLBACK >
 Simple way to execute a transaction with automatic retry.
 
template<typename... T>
constexpr void ignore_unused (T &&...) noexcept
 Suppress compiler warning about an unused item.
 
template<typename TO , typename FROM >
TO check_cast (FROM value, std::string_view description)
 Cast a numeric value to another type, or throw if it underflows/overflows.
 
void check_version () noexcept
 
thread_safety_model describe_thread_safety ()
 Describe thread safety available in this build.
 
template<PQXX_POTENTIAL_BINARY_ARG TYPE>
std::basic_string_view< std::byte > binary_cast (TYPE const &data)
 Cast binary data to a type that libpqxx will recognise as binary.
 
template<PQXX_CHAR_SIZED_ARG CHAR, typename SIZE >
std::basic_string_view< std::byte > binary_cast (CHAR const *data, SIZE size)
 Construct a type that libpqxx will recognise as binary.
 
constexpr zview operator""_zv (char const str[], std::size_t len) noexcept
 Support zview literals.
 
 PQXX_DECLARE_ENUM_CONVERSION (ExecStatusType)
 

Variables

template<typename TYPE >
std::string const type_name {internal::demangle_type_name(typeid(TYPE).name())}
 A human-readable name for a type, used in error messages and such.
 
constexpr from_table_t from_table
 Pass this to a stream_from constructor to stream table contents.
 
constexpr from_query_t from_query
 Pass this to a stream_from constructor to stream query results.
 
constexpr oid oid_none {0}
 The "null" oid.
 

Detailed Description

The home of all libpqxx classes, functions, templates, etc.

Transaction focus: types which monopolise a transaction's attention.

Copyright (c) 2000-2023, Jeroen T. Vermeulen.

See COPYING for copyright license. If you did not receive a file called COPYING with this source code, please notify the distributor of this mistake, or contact the author.

Handling of SQL arrays.

Copyright (c) 2000-2023, Jeroen T. Vermeulen.

See COPYING for copyright license. If you did not receive a file called COPYING with this source code, please notify the distributor of this mistake, or contact the author.

Implementation of the pqxx::result class and support classes.

pqxx::result represents the set of result rows from a database query

Copyright (c) 2000-2023, Jeroen T. Vermeulen.

See COPYING for copyright license. If you did not receive a file called COPYING with this source code, please notify the distributor of this mistake, or contact the author.

Typedef Documentation

◆ connection_base

Deprecated:
Old base class for connection. They are now the same class.

◆ field_size_type

using pqxx::field_size_type = typedef std::size_t

Number of bytes in a field of database data.

◆ fieldstream

using pqxx::fieldstream = typedef basic_fieldstream<char>
Deprecated:
Read a field using field::as<...>() or field::c_str().

◆ ilostream

using pqxx::ilostream = typedef basic_ilostream<char>

◆ large_object_size_type

using pqxx::large_object_size_type = typedef int64_t

Number of bytes in a large object.

◆ lostream

using pqxx::lostream = typedef basic_lostream<char>

◆ olostream

using pqxx::olostream = typedef basic_olostream<char>

◆ result_difference_type

using pqxx::result_difference_type = typedef int

Difference between result sizes.

◆ result_size_type

using pqxx::result_size_type = typedef int

Number of rows in a result set.

◆ row_difference_type

using pqxx::row_difference_type = typedef int

Difference between row sizes.

◆ row_size_type

using pqxx::row_size_type = typedef int

Number of fields in a row of database data.

◆ strip_t

template<typename TYPE >
using pqxx::strip_t = typedef std::remove_cv_t<std::remove_reference_t<TYPE> >

Remove any constness, volatile, and reference-ness from a type.

Deprecated:
In C++20 we'll replace this with std::remove_cvref.

◆ table_path

using pqxx::table_path = typedef std::initializer_list<std::string_view>

Representation of a PostgreSQL table path.

A "table path" consists of a table name, optionally prefixed by a schema name, which in turn is optionally prefixed by a database name.

A minimal example of a table path would be {mytable}. But a table path may also take the forms {myschema,mytable} or {mydb,myschema,mytable}.

◆ value_type

template<typename CONTAINER >
using pqxx::value_type = typedef strip_t<decltype(*std::begin(std::declval<CONTAINER>()))>

The type of a container's elements.

At the time of writing there's a similar thing in std::experimental, which we may or may not end up using for this.

Enumeration Type Documentation

◆ error_verbosity

enum class pqxx::error_verbosity : int
strong

Error verbosity levels.

Enumerator
terse 
normal 
verbose 

◆ format

enum class pqxx::format : int
strong

Format code: is data text or binary?

Binary-compatible with libpq's format codes.

Enumerator
text 
binary 

◆ isolation_level

Transaction isolation levels.

These are as defined in the SQL standard. But there are a few notes specific to PostgreSQL.

First, postgres does not support "read uncommitted." The lowest level you can get is "read committed," which is better. PostgreSQL is built on the MVCC paradigm, which guarantees "read committed" isolation without any additional performance overhead, so there was no point in providing the lower level.

Second, "repeatable read" also makes more isolation guarantees than the standard requires. According to the standard, this level prevents "dirty reads" and "nonrepeatable reads," but not "phantom reads." In postgres, it actually prevents all three.

Third, "serializable" is only properly supported starting at postgres 9.1. If you request "serializable" isolation on an older backend, you will get the same isolation as in "repeatable read." It's better than the "repeatable read" defined in the SQL standard, but not a complete implementation of the standard's "serializable" isolation level.

In general, a lower isolation level will allow more surprising interactions between ongoing transactions, but improve performance. A higher level gives you more protection from subtle concurrency bugs, but sometimes it may not be possible to complete your transaction without avoiding paradoxes in the data. In that case a transaction may fail, and the application will have to re-do the whole thing based on the latest state of the database. (If you want to retry your code in that situation, have a look at the transactor framework.)

Study the levels and design your application with the right level in mind.

Enumerator
read_committed 
repeatable_read 
serializable 

◆ skip_init

enum pqxx::skip_init : int

Flags for skipping initialisation of SSL-related libraries.

When a running process makes its first SSL connection to a database through libpqxx, libpq automatically initialises the OpenSSL and libcrypto libraries. But there are scenarios in which you may want to suppress that.

This enum is a way to express this. Pass values of this enum to pqxx::skip_init_ssl as template arguments.

Enumerator
nothing 

A do-nothing flag that does not affect anything.

openssl 

Skip initialisation of OpenSSL library.

crypto 

Skip initialisation of libcrypto.

◆ write_policy

enum class pqxx::write_policy
strong

Should a transaction be read-only, or read-write?

No, this is not an isolation level. So it really doesn't belong here. But it's not really worth a separate header.

Enumerator
read_only 
read_write 

Function Documentation

◆ binary_cast() [1/2]

template<PQXX_CHAR_SIZED_ARG CHAR, typename SIZE >
std::basic_string_view< std::byte > pqxx::binary_cast ( CHAR const *  data,
SIZE  size 
)

Construct a type that libpqxx will recognise as binary.

Takes a data pointer and a size, without being too strict about their types, and constructs a std::basic_string_view<std::byte> pointing to the same data.

This makes it a little easier to turn binary data, in whatever form you happen to have it, into binary data as libpqxx understands it.

◆ binary_cast() [2/2]

template<PQXX_POTENTIAL_BINARY_ARG TYPE>
std::basic_string_view< std::byte > pqxx::binary_cast ( TYPE const &  data)

Cast binary data to a type that libpqxx will recognise as binary.

There are many different formats for storing binary data in memory. You may have yours as a std::string, or a std::vector<uchar_t>, or one of many other types.

But for libpqxx to recognise your data as binary, it needs to be a std::basic_string<std::byte>, or a std::basic_string_view<std::byte>; or in C++20 or better, any contiguous block of std::byte.

Use binary_cast as a convenience helper to cast your data as a std::basic_string_view<std::byte>.

Warning
There are two things you should be aware of! First, the data must be contiguous in memory. In C++20 the compiler will enforce this, but in C++17 it's your own problem. Second, you must keep the object where you store the actual data alive for as long as you might use this function's return value.

Referenced by pqxx::connection::esc_raw(), pqxx::string_traits< binarystring >::into_buf(), pqxx::connection::quote_raw(), pqxx::transaction_base::quote_raw(), and pqxx::transaction_base::quote_raw().

◆ check_cast()

template<typename TO , typename FROM >
TO pqxx::check_cast ( FROM  value,
std::string_view  description 
)

Cast a numeric value to another type, or throw if it underflows/overflows.

Both types must be arithmetic types, and they must either be both integral or both floating-point types.

References pqxx::internal::cat2(), pqxx::internal::cmp_greater(), and ignore_unused().

◆ check_version()

void pqxx::check_version ( )
noexcept

Check library version at link time.

Ensures a failure when linking an application against a radically different libpqxx version than the one against which it was compiled.

Sometimes application builds fail in unclear ways because they compile using headers from libpqxx version X, but then link against libpqxx binary version Y. A typical scenario would be one where you're building against a libpqxx which you have built yourself, but a different version is installed on the system.

The check_library_version template is declared for any library version, but only actually defined for the version of the libpqxx binary against which the code is linked.

If the library binary is a different version than the one declared in these headers, then this call will fail to link: there will be no definition for the function with these exact template parameter values. There will be a definition, but the version in the parameter values will be different.

References ignore_unused(), and pqxx::internal::PQXX_VERSION_CHECK().

Referenced by pqxx::connection::connection().

◆ composite_into_buf()

template<typename... T>
char * pqxx::composite_into_buf ( char *  begin,
char *  end,
T const &...  fields 
)

Render a series of values as a single composite SQL value.

Warning
This code is still experimental. Use with care.

You may use this as a helper while implementing your own string_traits for a composite type.

References composite_size_buffer().

◆ composite_size_buffer()

template<typename... T>
std::size_t pqxx::composite_size_buffer ( T const &...  fields)
noexcept

Estimate the buffer size needed to represent a value of a composite type.

Returns a conservative estimate.

References pqxx::internal::empty_composite_str.

Referenced by composite_into_buf().

◆ describe_thread_safety()

pqxx::thread_safety_model PQXX_COLD pqxx::describe_thread_safety ( )

◆ encrypt_password() [1/2]

std::string PQXX_COLD pqxx::encrypt_password ( char const  user[],
char const  password[] 
)

◆ encrypt_password() [2/2]

std::string pqxx::encrypt_password ( zview  user,
zview  password 
)

Encrypt password.

Deprecated:
Use connection::encrypt_password instead.

References pqxx::zview::c_str(), and encrypt_password().

◆ field::as< std::string_view >() [1/2]

template<>
std::string_view pqxx::field::as< std::string_view > ( ) const

◆ field::as< std::string_view >() [2/2]

template<>
std::string_view pqxx::field::as< std::string_view > ( std::string_view const &  default_value) const

◆ field::to< std::string >() [1/2]

template<>
bool pqxx::field::to< std::string > ( std::string &  obj) const

◆ field::to< std::string >() [2/2]

template<>
bool pqxx::field::to< std::string > ( std::string &  obj,
std::string const &  default_value 
) const

◆ field::to< std::string_view >() [1/2]

template<>
bool pqxx::field::to< std::string_view > ( std::string_view &  obj) const

◆ field::to< std::string_view >() [2/2]

template<>
bool pqxx::field::to< std::string_view > ( std::string_view &  obj,
std::string_view const &  default_value 
) const

◆ from_string()

template<typename T >
T pqxx::from_string ( field const &  value)

Convert a field's value to type T.

Unlike the "regular" from_string, this knows how to deal with null values.

References pqxx::field::is_null(), pqxx::internal::throw_null_conversion(), and pqxx::field::view().

Referenced by pqxx::field::to().

◆ from_string< std::nullptr_t >()

template<>
std::nullptr_t pqxx::from_string< std::nullptr_t > ( field const &  value)

Convert a field's value to nullptr_t.

Yes, you read that right. This conversion does nothing useful. It always returns nullptr.

Except... what if the field is not null? In that case, this throws conversion_error.

References pqxx::field::is_null().

◆ ignore_unused()

template<typename... T>
constexpr void pqxx::ignore_unused ( T &&  ...)
constexprnoexcept

Suppress compiler warning about an unused item.

Referenced by pqxx::params::append(), check_cast(), check_version(), pqxx::stream_from::complete(), and pqxx::internal::error_string().

◆ oops_forbidden_conversion()

template<typename TYPE >
void pqxx::oops_forbidden_conversion ( )
noexcept

Nonexistent function to indicate a disallowed type conversion.

There is no implementation for this function, so any reference to it will fail to link. The error message will mention the function name and its template argument, as a deliberate message to an application developer that their code is attempting to use a deliberately unsupported conversion.

There are some C++ types that you may want to convert to or from SQL values, but which libpqxx deliberately does not support. Take char for example: we define no conversions for that type because it is not inherently clear whether whether the corresponding SQL type should be a single-character string, a small integer, a raw byte value, etc. The intention could differ from one call site to the next.

If an application attempts to convert these types, we try to make sure that the compiler will issue an error involving this function name, and mention the type, as a hint as to the reason.

◆ operator""_zv()

constexpr zview pqxx::operator""_zv ( char const  str[],
std::size_t  len 
)
constexprnoexcept

Support zview literals.

You can "import" this selectively into your namespace, without pulling in all of the pqxx namespace:

using pqxx::operator"" _zv;

◆ operator+()

const_row_iterator pqxx::operator+ ( const_row_iterator::difference_type  o,
const_row_iterator const &  i 
)
noexcept

◆ operator<<()

template<typename CHAR >
std:: basic_ostream< CHAR > & pqxx::operator<< ( std::basic_ostream< CHAR > &  s,
field const &  value 
)

Write a result field to any type of stream.

Deprecated:
The C++ streams library is not great to work with. In particular, error handling is easy to get wrong. So you're probably better off doing this by hand.

This can be convenient when writing a field to an output stream. More importantly, it lets you write a field to e.g. a stringstream which you can then use to read, format and convert the field in ways that to() does not support.

Example: parse a field into a variable of the nonstandard "<tt>long long</tt>" type.

extern result R;
long long L;
stringstream S;
// Write field's string into S
S << R[0][0];
// Parse contents of S into L
S >> L;
Result set containing data returned by a query or command.
Definition result.hxx:73

◆ parse_composite() [1/2]

template<typename... T>
void pqxx::parse_composite ( pqxx::internal::encoding_group  enc,
std::string_view  text,
T &...  fields 
)

Parse a string representation of a value of a composite type.

Warning
This code is still experimental. Use with care.

You may use this as a helper while implementing your own string_traits for a composite type.

This function interprets text as the string representation of a value of some composite type, and sets each of fields to the respective values of its fields. The field types must be copy-assignable.

The number of fields must match the number of fields in the composite type, and there must not be any other text in the input. The function is meant to handle any value string that the backend can produce, but not necessarily every valid alternative spelling.

Fields in composite types can be null. When this happens, the C++ type of the corresponding field reference must be of a type that can handle nulls. If you are working with a type that does not have an inherent null value, such as e.g. int, consider using std::optional.

References pqxx::internal::get_glyph_scanner(), and text.

Referenced by pqxx::field::composite_to(), and parse_composite().

◆ parse_composite() [2/2]

template<typename... T>
void pqxx::parse_composite ( std::string_view  text,
T &...  fields 
)

Parse a string representation of a value of a composite type.

Warning
This version only works for UTF-8 and single-byte encodings.

For proper encoding support, use the composite-type support in the field class.

References parse_composite(), and text.

◆ perform()

template<typename TRANSACTION_CALLBACK >
auto pqxx::perform ( TRANSACTION_CALLBACK &&  callback,
int  attempts = 3 
) -> std::invoke_result_t<TRANSACTION_CALLBACK>

Simple way to execute a transaction with automatic retry.

Executes your transaction code as a callback. Repeats it until it completes normally, or it throws an error other than the few libpqxx-generated exceptions that the framework understands, or after a given number of failed attempts, or if the transaction ends in an "in-doubt" state.

(An in-doubt state is one where libpqxx cannot determine whether the server finally committed a transaction or not. This can happen if the network connection to the server is lost just while we're waiting for its reply to a "commit" statement. The server may have completed the commit, or not, but it can't tell you because there's no longer a connection.

Using this still takes a bit of care. If your callback makes use of data from the database, you'll probably have to query that data within your callback. If the attempt to perform your callback fails, and the framework tries again, you'll be in a new transaction and the data in the database may have changed under your feet.

Also be careful about changing variables or data structures from within your callback. The run may still fail, and perhaps get run again. The ideal way to do it (in most cases) is to return your result from your callback, and change your program's data state only after perform completes successfully.

Parameters
callbackTransaction code that can be called with no arguments.
attemptsMaximum number of times to attempt performing callback. Must be greater than zero.
Returns
Whatever your callback returns.

◆ PQXX_DECLARE_ENUM_CONVERSION()

pqxx::PQXX_DECLARE_ENUM_CONVERSION ( ExecStatusType  )

◆ separated_list() [1/5]

template<typename CONTAINER >
auto pqxx::separated_list ( std::string_view  sep,
CONTAINER const &  c 
) -> typename std::enable_if< (not std::is_void<decltype(std::begin(c))>::value and not std::is_void<decltype(std::end(c))>::value), std::string>::type

Render items in a container as a string, using given separator.

References separated_list().

◆ separated_list() [2/5]

template<typename ITER >
std::string pqxx::separated_list ( std::string_view  sep,
ITER  begin,
ITER  end 
)

Render sequence as a string, using given separator between items.

References separated_list().

◆ separated_list() [3/5]

template<typename ITER , typename ACCESS >
std::string pqxx::separated_list ( std::string_view  sep,
ITER  begin,
ITER  end,
ACCESS  access 
)

Represent sequence of values as a string, joined by a given separator.

Use this to turn e.g. the numbers 1, 2, and 3 into a string "1, 2, 3".

Parameters
sepseparator string (to be placed between items)
beginbeginning of items sequence
endend of items sequence
accessfunctor defining how to dereference sequence elements

References to_string().

Referenced by pqxx::connection::quote_columns(), pqxx::connection::quote_table(), separated_list(), separated_list(), and separated_list().

◆ separated_list() [4/5]

template<typename TUPLE , std::size_t INDEX = 0, typename std::enable_if<(INDEX<=std::tuple_size< TUPLE >::value), int >::type = 0>
std::string pqxx::separated_list ( std::string_view  sep,
TUPLE const &  t 
)

References separated_list().

◆ separated_list() [5/5]

template<typename TUPLE , std::size_t INDEX = 0, typename ACCESS , typename std::enable_if<(INDEX==std::tuple_size< TUPLE >::value - 1), int >::type = 0>
std::string pqxx::separated_list ( std::string_view  sep,
TUPLE const &  t,
ACCESS const &  access 
)

Render items in a tuple as a string, using given separator.

References to_string().

◆ skip_init_ssl()

template<skip_init... SKIP>
void pqxx::skip_init_ssl ( )
noexcept

Control initialisation of OpenSSL and libcrypto libraries.

By default, libpq initialises the openssl and libcrypto libraries when your process first opens an SSL connection to a database. But this may not be what you want: perhaps your application (or some other library it uses) already initialises one or both of these libraries.

Call this function to stop libpq from initialising one or the other of these. Pass as arguments each of the skip_init flags for which of the libraries whose initialisation you want to prevent.

Warning
Each call to this function overwrites the effects of any previous call. So if you make one call to skip OpenSSL initialisation, and then another to skip libcrypto initialisation, the first call will do nothing.

Examples:

  • To let libpq initialise libcrypto but not OpenSSL: skip_init_ssl<pqxx::skip_init::openssl>();
  • To let libpq know that it should not initialise either:
    skip_init_ssl<pqxx::skip_init::openssl, pqxx::skip_init::crypto>();
  • To say explicitly that you want libpq to initialise both: skip_init_ssl<pqxx::skip_init::nothing>();

References pqxx::internal::skip_init_ssl().

◆ to_string()

template<>
std::string pqxx::to_string ( field const &  value)

◆ transaction_base::query_value< std::string_view >()

template<>
std::string_view pqxx::transaction_base::query_value< std::string_view > ( zview  query,
std::string_view  desc 
)
delete

Forbidden specialisation: underlying buffer immediately goes out of scope.

Variable Documentation

◆ from_query

constexpr from_query_t pqxx::from_query
constexpr

Pass this to a stream_from constructor to stream query results.

Deprecated:
Use transaction_base::stream instead of stream_from.

Referenced by pqxx::stream_from::query().

◆ from_table

constexpr from_table_t pqxx::from_table
constexpr

Pass this to a stream_from constructor to stream table contents.

Deprecated:
Use transaction_base::stream instead of stream_from.

Referenced by pqxx::stream_from::raw_table().

◆ oid_none

◆ type_name

template<typename TYPE >
std::string const pqxx::type_name {internal::demangle_type_name(typeid(TYPE).name())}

A human-readable name for a type, used in error messages and such.

Actually this may not always be very user-friendly. It uses std::type_info::name(). On gcc-like compilers we try to demangle its output. Visual Studio produces human-friendly names out of the box.

This variable is not inline. Inlining it gives rise to "memory leak" warnings from asan, the address sanitizer, possibly from use of std::type_info::name.