Acq vandelay uploads are very slow

[Chris Sharp]

Found on a mostly-realistic 2.12.4 test server:

When using the Load MARC Order Records feature from the Acquisitions menu, and uploading a set of 53 records creating copies and using a match set[1], the load takes nearly thirty minutes. Investigation reveals that the bottleneck comes from the vandelay.match_set_test_marcxml function, which is triggered by an insert into vandelay.queued_bib_record.

[1] match set parameters in this case:

evergreen=# select * from vandelay.match_set_point where match_set = 3;
 id | match_set | parent | bool_op | svf | tag | subfield | negate | quality | heading
----+-----------+--------+---------+-----------+-----+----------+--------+---------+---------
 70 | 3 | | AND | | | | f | 1 | f
 71 | 3 | 70 | OR | | | | f | 1 | f
 72 | 3 | 71 | | | 020 | a | f | 2 | f
 73 | 3 | 71 | | | 022 | a | f | 2 | f
 74 | 3 | 71 | | | 024 | a | f | 2 | f
 75 | 3 | 71 | | | 028 | a | f | 2 | f
 76 | 3 | 70 | | bib_level | | | f | 16 | f
 77 | 3 | 70 | | item_type | | | f | 16 | f

I will attach the query and explain analyze results below.

Evergreen 2.12.4
OpenSRF 2.5.0
PostgreSQL 9.4
Ubuntu 14.04 LTS