libpqxx
7.7.0
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"Stateless cursor" class: easy API for retrieving parts of result sets More...
#include <cursor.hxx>
Public Types | |
using | size_type = result_size_type |
using | difference_type = result_difference_type |
Public Member Functions | |
stateless_cursor (transaction_base &tx, std::string_view query, std::string_view cname, bool hold) | |
Create cursor. More... | |
stateless_cursor (transaction_base &tx, std::string_view adopted_cursor) | |
Adopt an existing scrolling SQL cursor. More... | |
void | close () noexcept |
Close this cursor. More... | |
size_type | size () |
Number of rows in cursor's result set. More... | |
result | retrieve (difference_type begin_pos, difference_type end_pos) |
Retrieve rows from begin_pos (inclusive) to end_pos (exclusive) More... | |
std::string const & | name () const noexcept |
Return this cursor's name. More... | |
"Stateless cursor" class: easy API for retrieving parts of result sets
This is a front-end for SQL cursors, but with a more C++-like API.
Actually, stateless_cursor feels entirely different from SQL cursors. You don't keep track of positions, fetches, and moves; you just say which rows you want. See the retrieve() member function.
using pqxx::stateless_cursor< up, op >::difference_type = result_difference_type |
using pqxx::stateless_cursor< up, op >::size_type = result_size_type |
pqxx::stateless_cursor< up, op >::stateless_cursor | ( | transaction_base & | tx, |
std::string_view | query, | ||
std::string_view | cname, | ||
bool | hold | ||
) |
Create cursor.
tx | The transaction within which you want to create the cursor. |
query | The SQL query whose results the cursor should traverse. |
cname | A hint for the cursor's name. The actual SQL cursor's name will be based on this (though not necessarily identical). |
hold | Create a WITH HOLD cursor? Such cursors stay alive after the transaction has ended, so you can continue to use it. |
References pqxx::cursor_base::random_access.
pqxx::stateless_cursor< up, op >::stateless_cursor | ( | transaction_base & | tx, |
std::string_view | adopted_cursor | ||
) |
Adopt an existing scrolling SQL cursor.
This lets you define a cursor yourself, and then wrap it in a libpqxx-managed stateless_cursor
object.
tx | The transaction within which you want to manage the cursor. |
adopted_cursor | Your cursor's SQL name. |
References pqxx::cursor_base::backward_all().
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noexcept |
Close this cursor.
The destructor will do this for you automatically.
Closing a cursor is idempotent. Closing a cursor that's already closed does nothing.
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noexcept |
Return this cursor's name.
result pqxx::stateless_cursor< up, op >::retrieve | ( | difference_type | begin_pos, |
difference_type | end_pos | ||
) |
Retrieve rows from begin_pos (inclusive) to end_pos (exclusive)
Rows are numbered starting from 0 to size()-1.
begin_pos | First row to retrieve. May be one row beyond the end of the result set, to avoid errors for empty result sets. Otherwise, must be a valid row number in the result set. |
end_pos | Row up to which to fetch. Rows are returned ordered from begin_pos to end_pos, i.e. in ascending order if begin_pos < end_pos but in descending order if begin_pos > end_pos. The end_pos may be arbitrarily inside or outside the result set; only existing rows are included in the result. |
size_type pqxx::stateless_cursor< up, op >::size | ( | ) |
Number of rows in cursor's result set.