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Hash Key Disappearance

Hash Key Disappearance

Hash Key Disappearance

I've inherited the following perl code fragment....

 1   %Returned = dbPrepare( %Input );
 2   if ( $Returned{nStatus} == 0 ) {
 3        %Input = ( nDbCursor => $Returned{nDbCursor} );
 4        %Returned = dbExecute( %Input );
 5   }
 6   if ( $Returned{nStatus} == 0 ) {
 7        # FINISH CURSOR
 8        %Input = ( nDbCursor => $Returned{nDbCursor} );
 9        %Returned = dbFinish( %Input );
10   }
12   if ( $Returned{nStatus} == 0 ) {
13        %Returned = (
14             nStatus => 0,
15             nReturnCode => 0,
16             sReturnDesc => "erLogDataError:  Successful"
17        );
18   }
19   return( %Returned );

My environment: AIX 4.3.3, perl 5.004_04

The subroutine dbPrepare (line 1) returns a hash table with 4 keys (nStatus, nReturnCode, sReturnDesc, and nDbCursor).

The subroutine dbExecute (line 4) returns a hash table with 3 keys (nStatus, nReturnCode, and sReturnDesc).

The subroutine dbFinish (line 9) returns a hash table with 3 keys (nStatus, nReturnCode, and sReturnDesc).

I haven't been able to detect a pattern, yet, but sometimes the value of nDbCursor (on line 8) is null. If it happened every time, I would deduce that the key nDbCursor became undefined after the execution of dbExecute. Shouldn't the key nDbCursor still be available within the hash table Returned after the execution of dbExecute (and dbFinish)?

As a fix, I am planning to save the value of nDbCursor in a variable after executing dbPrepare and using the variable for the resetting of the hash Input. I'm trying to understand why this code sometimes works and sometimes fails. Any enlightenment would be greatly appreciated.


RE: Hash Key Disappearance

nDbCursor is just a bareword hash key.  Do you mean
that $Returned{nDbCursor} is Null?

Line 1 sets %Returned much the same as the following:

 %Returned = ( nStatus => someval,
               nReturnCode => someval,
               nReturnDesc => someval,
               nDbCursor => someval

Line 4 (if executed) sets %Returned much like:

 %Returned = ( nStatus => someval,
               nReturnCode => someval,
               nReturnDesc => someval

If the Line 4 statement has been executed, then
 %Returned{nDbCursor} should be undefined.  The
 assignment in Line 4 is setting the entire hash,
 not just reassigning to $Returned{nStatus},
 $Returned{nReturnCode}, and $Returned{nReturnDesc}
 All the old hash keys and values are tossed.

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