Re: [BUGS] BUG #14155: bloom index error with unlogged table - Mailing list pgsql-hackers

From David G. Johnston
Subject Re: [BUGS] BUG #14155: bloom index error with unlogged table
Date
Msg-id CAKFQuwa9UTHvc-6EH3+wkyfwGLdZ4m0KAZ44BHpr-QxE=tV9mQ@mail.gmail.com
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In response to Re: [BUGS] BUG #14155: bloom index error with unlogged table  (Michael Paquier <michael.paquier@gmail.com>)
List pgsql-hackers
On Tue, Jun 7, 2016 at 1:35 AM, Michael Paquier <michael.paquier@gmail.com> wrote:
On Fri, Jun 3, 2016 at 11:25 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Michael Paquier <michael.paquier@gmail.com> writes:
>> Actually, the docs could be more polished.
>
> I think the docs could stand to be rewritten from scratch ;-).  But
> upthread there was an offer to work on them if we made the code behavior
> saner.  I've done the latter part, I don't want to do the former.

I have finally given a shot at improving the docs with the attached.
Comments are welcome.

​Looks good.  Thanks!​

​Some minor word-smithing​ related stuff and one definitional concern:

​"of all indexed attributes and so it can report false positives" -> of all indexed attributes and as such is prone to reporting false positives;

​"in the set, however" -> "in the set although"
​"one only needs a single bloom index (default 80, maximum 4096)" -> ​the default seems like it would be better placed in the first paragraph of the intro where "whose size in calculated in bits" is mentioned; or better yet dropped altogether since the parameters section covers the defaults.

*** "to the number of the column for" - the examples imply that each parameter refers to columns by name, not number.

"a bloom index  representing first the advantage to be more" - this intro to the example needs some work.  maybe: "Here is a more complete example of index definition and usage, as well as a comparison with the equivalent btree index.  The bloom index is considerably smaller as well as performs better than the btree index.

---As an aside, is a multi-column index really a fair comparison here?

---Leaving a sequential scan explain analyze in place should be considered.

​"The Bloom opclass interface" -> The Bloom opclass interface requires a hash function for the indexing datatype and an equality operator for searching.  The example...(drop the simple conclusion the word the equality operator part better).

​"are implemented with the module" - are supplied by this module. (side question, for 10.0 how about we call these extensions instead of modules?)

David J.


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