Re: [HACKERS] strange behavior of UPDATE

Edmund Mergl <E.Mergl@bawue.de> writes:
> The table is filled with 1.000.000 rows of random data
> and on every field an index is created.

BTW, do you happen to know just how random the data actually is?
I noticed that the update queryupdate bench set k500k = k500k + 1 where k100 = 30;
updates 10,000 rows.  If this "random" data actually consists of
10,000 repetitions of only 100 distinct values in every column,
then a possible explanation for the problem would be that our
btree index code isn't very fast when there are large numbers of
identical keys.  (Mind you, I have no idea if that's true or not,
I'm just trying to think of likely trouble spots.  Anyone know
btree well enough to say whether that is likely to be a problem?)
        regards, tom lane