libpqxx
7.9.0
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Result set containing data returned by a query or command. More...
#include <result.hxx>
Public Types | |
using | size_type = result_size_type |
using | difference_type = result_difference_type |
using | reference = row |
using | const_iterator = const_result_iterator |
using | pointer = const_iterator |
using | iterator = const_iterator |
using | const_reverse_iterator = const_reverse_result_iterator |
using | reverse_iterator = const_reverse_iterator |
Public Member Functions | |
result () noexcept | |
result (result const &rhs) noexcept=default | |
result (result &&rhs) noexcept=default | |
result & | operator= (result const &rhs) noexcept=default |
Assign one result to another. More... | |
result & | operator= (result &&rhs) noexcept=default |
Assign one result to another, invaliding the old one. More... | |
Comparisons | |
You can compare results for equality. Beware: this is a very strict, dumb comparison. The smallest difference between two results (such as a string "Foo" versus a string "foo") will make them unequal. | |
bool | operator== (result const &) const noexcept |
Compare two results for equality. More... | |
bool | operator!= (result const &rhs) const noexcept |
Compare two results for inequality. More... | |
template<typename... TYPE> | |
auto | iter () const |
Iterate rows, reading them directly into a tuple of "TYPE...". More... | |
const_reverse_iterator | rbegin () const |
const_reverse_iterator | crbegin () const |
const_reverse_iterator | rend () const |
const_reverse_iterator | crend () const |
const_iterator | begin () const noexcept |
const_iterator | cbegin () const noexcept |
const_iterator | end () const noexcept |
const_iterator | cend () const noexcept |
reference | front () const noexcept |
reference | back () const noexcept |
PQXX_PURE size_type | size () const noexcept |
PQXX_PURE bool | empty () const noexcept |
size_type | capacity () const noexcept |
void | swap (result &) noexcept |
Exchange two result values in an exception-safe manner. More... | |
row | operator[] (size_type i) const noexcept |
Index a row by number. More... | |
row | at (size_type) const |
Index a row by number, but check that the row number is valid. More... | |
field | at (size_type, row_size_type) const |
Index a field by row number and column number. More... | |
void | clear () noexcept |
Let go of the result's data. More... | |
Column information | |
class | pqxx::internal::gate::result_pipeline |
class | pqxx::field |
class | pqxx::internal::gate::result_creation |
class | pqxx::internal::gate::result_connection |
class | pqxx::internal::gate::result_row |
class | pqxx::internal::gate::result_sql_cursor |
PQXX_PURE row_size_type | columns () const noexcept |
Number of columns in result. More... | |
row_size_type | column_number (zview name) const |
Number of given column (throws exception if it doesn't exist). More... | |
char const * | column_name (row_size_type number) const & |
Name of column with this number (throws exception if it doesn't exist) More... | |
int | column_storage (row_size_type number) const |
Server-side storage size for field of column's type, in bytes. More... | |
int | column_type_modifier (row_size_type number) const noexcept |
Type modifier of the column with this number. More... | |
oid | column_type (row_size_type col_num) const |
Return column's type, as an OID from the system catalogue. More... | |
oid | column_type (zview col_name) const |
Return column's type, as an OID from the system catalogue. More... | |
oid | column_table (row_size_type col_num) const |
What table did this column come from? More... | |
oid | column_table (zview col_name) const |
What table did this column come from? More... | |
row_size_type | table_column (row_size_type col_num) const |
What column in its table did this column come from? More... | |
row_size_type | table_column (zview col_name) const |
What column in its table did this column come from? More... | |
PQXX_PURE std::string const & | query () const &noexcept |
Query that produced this result, if available (empty string otherwise) More... | |
PQXX_PURE oid | inserted_oid () const |
If command was an INSERT of 1 row, return oid of the inserted row. More... | |
PQXX_PURE size_type | affected_rows () const |
If command was INSERT , UPDATE , or DELETE : number of affected rows. More... | |
template<typename CALLABLE > | |
void | for_each (CALLABLE &&func) const |
Run func on each row, passing the row's fields as parameters. More... | |
Result set containing data returned by a query or command.
This behaves as a container (as defined by the C++ standard library) and provides random access const iterators to iterate over its rows. You can also access a row by indexing a result R
by the row's zero-based number:
for (result::size_type i=0; i < std::size(R); ++i) Process(R[i]);
Result sets in libpqxx are lightweight, reference-counted wrapper objects which are relatively small and cheap to copy. Think of a result object as a "smart pointer" to an underlying result set.
using pqxx::result::const_iterator = const_result_iterator |
using pqxx::result::const_reverse_iterator = const_reverse_result_iterator |
using pqxx::result::iterator = const_iterator |
using pqxx::result::pointer = const_iterator |
using pqxx::result::reference = row |
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noexcept |
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defaultnoexcept |
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defaultnoexcept |
pqxx::result::size_type pqxx::result::affected_rows | ( | ) | const |
If command was INSERT
, UPDATE
, or DELETE
: number of affected rows.
INSERT
, UPDATE
, or DELETE
; zero for all other commands. Index a row by number, but check that the row number is valid.
pqxx::field pqxx::result::at | ( | size_type | row_num, |
pqxx::row_size_type | col_num | ||
) | const |
Index a field by row number and column number.
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noexcept |
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noexcept |
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noexcept |
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noexcept |
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noexcept |
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noexcept |
Let go of the result's data.
Use this if you need to deallocate the result data earlier than you can destroy the result
object itself.
Multiple result
objects can refer to the same set of underlying data. The underlying data will be deallocated once all result
objects that refer to it are cleared or destroyed.
char const * pqxx::result::column_name | ( | row_size_type | number | ) | const & |
Name of column with this number (throws exception if it doesn't exist)
Referenced by pqxx::field::name().
pqxx::row::size_type pqxx::result::column_number | ( | zview | name | ) | const |
Number of given column (throws exception if it doesn't exist).
References pqxx::zview::c_str().
Referenced by pqxx::row::column_number().
int pqxx::result::column_storage | ( | row_size_type | number | ) | const |
Server-side storage size for field of column's type, in bytes.
Returns the size of the server's internal representation of the column's data type. A negative value indicates the data type is variable-length.
pqxx::oid pqxx::result::column_table | ( | row_size_type | col_num | ) | const |
What table did this column come from?
References pqxx::oid_none.
oid pqxx::result::column_table | ( | zview | col_name | ) | const |
What table did this column come from?
pqxx::oid pqxx::result::column_type | ( | row_size_type | col_num | ) | const |
Return column's type, as an OID from the system catalogue.
References pqxx::oid_none.
oid pqxx::result::column_type | ( | zview | col_name | ) | const |
Return column's type, as an OID from the system catalogue.
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noexcept |
Type modifier of the column with this number.
The meaning of modifier values is type-specific; they typically indicate precision or size limits.
Use this only if you know what you're doing. Most applications do not need it, and most types do not use modifiers.
The value -1 indicates "no information available."
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noexcept |
Number of columns in result.
pqxx::result::const_reverse_iterator pqxx::result::crbegin | ( | ) | const |
pqxx::result::const_reverse_iterator pqxx::result::crend | ( | ) | const |
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noexcept |
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noexcept |
void pqxx::result::for_each | ( | CALLABLE && | func | ) | const |
Run func
on each row, passing the row's fields as parameters.
Goes through the rows from first to last. You provide a callable func
.
For each row in the result
, for_each
will call func
. It converts the row's fields to the types of func
's parameters, and pass them to func
.
(Therefore func
must have a single signature. It can't be a generic lambda, or an object of a class with multiple overloaded function call operators. Otherwise, for_each
will have no way to detect a parameter list without ambiguity.)
If any of your parameter types is std::string_view
, it refers to the underlying storage of this result
.
If any of your parameter types is a reference type, its argument will refer to a temporary value which only lives for the duration of that single invocation to func
. If the reference is an lvalue reference, it must be const
.
For example, this queries employee names and salaries from the database and prints how much each would like to earn instead:
If func
throws an exception, processing stops at that point and propagates the exception.
pqxx::usage_error | if func 's number of parameters does not match the number of columns in this result. |
The parameter types must have conversions from PostgreSQL's string format defined; see Supporting additional data types.
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noexcept |
pqxx::oid pqxx::result::inserted_oid | ( | ) | const |
If command was an INSERT
of 1 row, return oid of the inserted row.
auto pqxx::result::iter | ( | ) | const |
Iterate rows, reading them directly into a tuple of "TYPE...".
Converts the fields to values of the given respective types.
Use this only with a ranged "for" loop. The iteration produces std::tuple<TYPE...> which you can "unpack" to a series of auto
variables.
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noexcept |
Compare two results for inequality.
Assign one result to another, invaliding the old one.
Assign one result to another.
Copying results is cheap: it copies only smart pointers, but the actual data stays in the same place.
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noexcept |
Compare two results for equality.
Index a row by number.
This returns a row object. Generally you should not keep the row around as a variable, but if you do, make sure that your variable is a row
, not a row&
.
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noexcept |
Query that produced this result, if available (empty string otherwise)
pqxx::result::const_reverse_iterator pqxx::result::rbegin | ( | ) | const |
pqxx::result::const_reverse_iterator pqxx::result::rend | ( | ) | const |
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noexcept |
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noexcept |
Exchange two result
values in an exception-safe manner.
If the swap fails, the two values will be exactly as they were before.
The swap is not necessarily thread-safe.
pqxx::row::size_type pqxx::result::table_column | ( | row_size_type | col_num | ) | const |
What column in its table did this column come from?
References pqxx::to_string().
row_size_type pqxx::result::table_column | ( | zview | col_name | ) | const |
What column in its table did this column come from?
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