circular reference in DBI::DBD::SqlEngine::TieTables

[rwfranks]

Transcribed verbatim from CPAN RT#125590, warts and all.

Fri Jun 15 08:46:50 2018 davem [...] iabyn.com - Ticket created
Subject: circular reference in DBI::DBD::SqlEngine::TieTables

Date: Fri, 15 Jun 2018 13:46:32 +0100
To: [email protected]
From: Dave Mitchell [email protected]

While debugging an issue with DBD::CSV and/or perl:

https://rt.perl.org/Ticket/Display.html?id=133270

I spotted code in DBI::DBD::SqlEngine::TieTables which appears to
be creating a circular reference, and thus leaking.

DBI::DBD::SqlEngine::TieTables::TIEHASH() creates a tie object hash,
one of whose entries is a reference back to the $dbh handle.

I don't understand this code well enough to be 100% certain its a leak,
but it sure looks like a weaken() is in order.

The following code definitely leaks, although that may be in part due to
a bug in Text::CSV_XS which I have reported separately:

(it requires editing 'f_dir' to point to an untarred DBD-CSV-0.53
directory)

    use strict;
    use warnings;

    use DBI;

    while (1) {
        my $dbh = DBI->connect ("dbi:CSV:", undef, undef, {
            f_schema         => undef,
            f_dir            => '/home/davem/tmp-nobackup/dbd-csv-free/DBD-CSV-0.53/t',
            f_dir_search     => [],
            f_ext            => ".csv/r",
            f_lock           => 2,
            f_encoding       => "utf8",

            csv_auto_diag => 0,

            RaiseError       => 1,
            PrintError       => 1,
            FetchHashKeyName => "NAME_lc",
            }) or die "$DBI::errstr\n" || $DBI::errstr;
    }

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