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Re: Speeding up the DBI

by spazm (Monk)
on Dec 17, 2008 at 20:57 UTC ( #731056=note: print w/replies, xml ) Need Help??

in reply to Speeding up the DBI

The idiom listed above is slightly flawed, perhaps the behavior of fetchall_arrayref has changed in the last few years? Original:
my $rowcache; while (my $aref = shift(@$rowcache) || shift ( @{$rowcache= $sth->fetchall_arrayref(undef, $max_rows)} ) )
From perldoc DBI:
Here’s an example (assumes RaiseError is enabled): my $rows = []; # cache for batches of rows while( my $row = ( shift(@$rows) || # get row from cache, or +reload cache: shift(@{$rows=$sth->fetchall_arrayref(unde +f,10_000)||[]}) ) ) { ... }
The difference being:  || [] . fetchall_arrayref is returning undef instead of an empty arrayref.

The original code as listed will give an annoying "attempt to use undefined value as an ARRAYREF" style error after processing the last line of sql output.

The error line will be attributed to the last line of the while loop since the error happens in the while loop comparator.

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[stevieb]: 16.96 hours of runtime of a Raspberry Pi on a 12v, 7.2Ah battery :) Now to watch now long it takes to recharge the battery completely with my 18v solar cells in the sun :)
[stevieb]: my high-range estimate was 18 hours
[stevieb]: battery was at about 95% capacity when the test began
[stevieb]: in the meantime while it was on battery, I got my shift register issues fixed, as well as certain interrupt issues

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