Tom Lane wrote:
Mladen Gogala <mladen.gogala@xxxxxxxxxxx> writes:
The number of rows is significantly smaller, but the table contains
rather significant "text" field which consumes quite a bit of TOAST
storage and the sizes are comparable. Postgres read through 27GB in 113
seconds, less than 2 minutes and oracle took 2 minutes 37 seconds to
read through 35GB. I stand corrected: there is nothing wrong with the
speed of the Postgres sequential scan.
Um ... the whole point of TOAST is that the data isn't in-line.
So what Postgres was actually reading through was probably quite a
lot less than 27Gb. It's probably hard to make a completely
apples-to-apples comparison because the two databases are so different,
but I don't think this one proves that PG is faster than Oracle.
regards, tom lane
As is usually the case, you're right. I will try copying the table to
Postgres over the weekend, my management would not look kindly upon my
copying 35GB of the production data during the working hours, for the
scientific reasons. I have the storage and I can test, I will post the
result. I developed quite an efficient Perl script which does copying
without the intervening CSV file, so that the copy should not take more
than 2 hours. I will be able to impose a shared lock on the table over
the weekend, so that I don't blow away the UNDO segments.
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Mladen Gogala
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