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>5.11. Example - Asynchronous Queries</A
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>This example uses the experimental asynchronous query commands
described in <A
HREF="pgtcl-ref-async.html"
>Section 4.4</A
>.
It shows how a query could be sent to the database, and the
application could continue processing without blocking while
waiting for the results to come back. It also shows part of how
a Cancel button might be implemented.
Note: this is not a complete script.</P
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>Example 5-17. Asynchronous Queries</B
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>pg_sendquery $conn "SELECT * FROM tables... WHERE conditions ORDER BY ..."
# Wait for not-busy condition:
while {[pg_isbusy $conn]} {
... Do something here, like check for user input and update the interface...
... Good idea to insert a delay so it doesn't busy-wait ...
... Check for cancel button ...
if {$user_pressed_cancel_button} break
}
# Did the user hit the Cancel button? If so, try to cancel the query.
if {$user_pressed_cancel_button} {
pg_cancelrequest $conn
}
# Fetch results until it there are none left (even if canceled):
while {[set res [pg_getresult $conn]] != ""} {
if {!$user_pressed_cancel_button} {
... do something with the query result $res ...
}
pg_result $res -clear
} </PRE
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