Well, if you want to be as certain as you can - you're going to need to
stick to a fairly rigorous check. What you could do is export the DB
into something PHP can quickly load right in (something serialized, for
e.g.) every X minutes, and then at the end of the day run your 'rigorous
test'. One thing that (might) spare you, is once you've checked a set
against itself, you shouldn't need to check it again [depends on how
changes are handled]. If you track the records that are changed updated
or added, and every few hours (or nightly) check back over that - you'll
have a fairly fast performing system that has few likely dupes on the whole.
Now, in my opinion you might want to stick with the idea of hitting the
DB directly (depends) - but toss in some 'real world sanity checking'.
Without seeing the query, I can't say if you haven't already - but
chances are you can do quicker passes frequently, and occasionally do
the slower more thorough checks. Most peoples last names don't change
often - and when they do, they could easily also change phone number and
address. Toss in 'soundex' to handle typos if doing it at the DB level,
or you can use levenshtein distance [levenshtein()] to catch the
occasional typo if hitting the info in PHP.
Another thing to note - if you know you're going to have duplicates no
matter what your efforts, you might just want to automatically accept
new records and let the system mark anything that looks dupe for a human
to check over, saving you all that checking on the entry end of things
(which I guess are done in batches, PDA sync or some such?)
If you realize there will be no fast perfect solution, you can start
getting creative with a couple different levels and find a pretty happy
- Martin Norland, Sys Admin / Database / Web Developer, International
The opinion(s) contained within this email do not necessarily represent
those of St. Jude Children's Research Hospital.
[EMAIL PROTECTED] wrote:
We have a table with contacts and we need to determine if someone's already in
there but with possibly slightly different info or if the old data contains
duplicates. Current criteria (I'm sure there's better):
If home phone matches any existing home, work or alt phones.
If work phone matches any existing home, work or alt phones.
If alt phone matches any existing home, work or alt phones.
If a concat of last name, street address and zip match any existing.
Table currently contains about 60,000 entries (imported from old system) and we
can expect it to grow.
Indexes are on home, work and alt phones, as well as last name, street address
and zip. Tried it without indexes, it was slow.. tried it with indexes.. still
about the same speed.
Tried seeing if putting the dupe check into a prepared statement sped it up
any. It didn't.
Analyzed table. Same speed.
Out of 60,000 entries, we have roughly 40,000+ unique phone numbers (that's
doing a union on all three phone number columns). So even pre-compiling just
that list and querying another table is going to be similar in time issues it
For new contacts being brought in, we might have 30-60 at a time (maybe more)
so this query would end up being run on each of the 30-60. At 1.5-2 sec for
each query, that ends up being a full minute or two to do the whole scan.
If I pull the phone #'s and name/address/zip combies into an array in PHP first, it's
only like 12 secs, but each user would end up pulling it (and maybe store in a session
variable or something) and re-pull it periodically to make sure it's semi-fresh. This
sounds like the quicker, but not the "best" solution.
Any tricks, tips or philosophical and/or theoretical things I've just not
seeing, please let me know.
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