Re: Search efficiency - RDMS search versus free text search
Date: Wed, 14 Jan 2009 15:34:33 GMT
"paul c" <toledobythesea_at_oohay.ac> wrote in message
> Taras_96 wrote:
>> Hi everyone,
>> I just had an interesting discussion with a colleague regarding how we
>> are implementing search. We allow users to browse resources under a
>> list of topics, so for example a list of all resources relating to
>> 'cars'. One way of doing this is with a SQL query against the database
>> SELECT * FROM resources WHERE topic_area = 'cars'
>> The actual query is quite a bit more complicated than this (involves
>> table joins and the like).
>> However, he said that due to the table joins (coming from the fact
>> that the database is normalised), that this technique is quite
>> resource expensive. Instead, we are using the Google Search Appliance
>> to index our resources (delivered via the web), and creating the topic
>> pages by using Google to search on meta-data, which apparently results
>> in better performance.
>> This came to me somewhat as a suprise, as I was under the impression
>> that returning such result sets were one of the key uses of a RDMS -
>> the efficient storage and retrieval of records. I can understand the
>> performance issues if the search was a free text search, but the above
>> search is really searching against an indexed column value.
>> Is this often the case with enterprise level database searches - that
>> the database itself isn't used for searching because of performance
> I think this is a significant question even if it is perhaps naive in the
> c.d.t. context. The question I would ask is: does the 'appliance' give
> the same answers as the dbms? Possibly the answer to that question would
> indicate that the requirements for this particular database are just as
> fuzzy as the answers.
> Presumably, this is a read-only db at least as far as some users are
> concerned. If there is a requirement for accurate updating by other
> users, let's hope they use some version or special copy of the db itself.
> On the other hand, I remember read-only advertising research apps from the
> early 1980's that did fuzzy searching. Their main requirement was to give
> possible answers, not all answers.
> (Some time ago I was interested in finding the children of a woman I
> thought to be dead for twenty or more years. No criticism of Google but
> its algorithms got me nowhere whereas Yahoo gave me some clues as to
> countries she might have lived in. Knowing her husband's surname and the
> given name of her male child, I looked him up in a foreign telephone
> directory and by accident reached another son I didn't know of, and then
> to my surprise, the lady herself, still alive. At one time, Yahoo's
> machine-generated indexes were edited to some extent manually. No idea if
> this is still the case, but this example shows that the ranking involved
> in these 'search engines' may omit useful answers and has a big effect on
> subsequent searches.)
From reading your response, I have some real doubt as to whether it was the Google "algorithms" or the data those algorithms had available to them that caused the results you saw.
Speculating about the internals of an engine like Google provides lots of opportunities for mistakes. Google gets inputs from all over the place. Google applies algorithms to those inputs prior to storing. Google uses queries to get a presumably relevant subset back when responding to a user request. For this last purpose, the database can indeed be treated as read only, although there is probably a second schema that collects data about user search activities, and that schema is probably written to.
As far as fuzzy logic goes, the data can be fuzzed prior to storage, or fuzzed in the course of a query, or fuzzed by an algorithm applied to query results. Without know how the data is stored, we can't know whether it's already fuzzy in storage.
As far as the OP is concerned, I'd like some responder that's more well versed in theory than I am to refine the OP's understanding of what relational databases are for. "The efficient storage and retrieval or records" seems like the very tip of the iceberg to me. Received on Wed Jan 14 2009 - 16:34:33 CET