31337 vision express / super optyk [polish only]

znajomy zadzwonił i poprosił bym mu nagrał jakiś serial w tv.

nagrałem i w trakcje oglądania spojrzałem na reklamy. pojawiła się reklama “vision express" gdzie dają zniżki procentowo takie ile ma się lat.

reklama jak reklama, ale to co mnie całkiem powaliło to wygląd tej planszy do sprawdzania wzroku (litery różnej wielkości).

oto 2 “screenshoty" z tej reklamy:

shot1.jpg

shot2.jpg

drugie zdjęcie jest nieostre (kamera w reklamie była w ruchu), ale pokazuję, że na górze jest “O".

powstaje pytanie – czy ten co zatwierdzał reklamę zwrócił uwagę na żarcik? z treści reklamy nie wynika by miała być ona “z przymrużeniem oka".

avoiding “empty” updates

just recently i saw a very interesting situation.

one table in customer database (with about 1.5 milion rows) was *very often* updated. using series of simple:

update table set field = .., where id = ...

updates always updated 1 record, search was using primary key, so it was quite fast.

what was strange was the fact that the table get about 20 times more updates then the next most updated table.

after careful checking i found out that a lot (about 60-70%) of the updates actually didn't change anything!

they were simply setting values that were already there.

so, i started to think about hwo to avoid this kind of situation.

and this is what i found out.

Continue reading avoiding “empty" updates

(postgre)sql gotchas

i would like to write about a things that are not really errors by themselves – they are simply situations when database acts in undesired way. a way that's perfectly logical, but where the logic is not always clearly seen “at first sight".

so, don't expect any postgresql-bashing. if you want some, indicate so in comments, i'll find some things to bash postgresql for.

but in here i'd rather bash us – people – for making mistakes. the ones that are not really easy to see as mistakes for database.

Continue reading (postgre)sql gotchas

indexable “field like ‘%something'” – update

thomas reiss just published his follow up to my post about indexed searches in “like ‘%something'" cases.

i don't understand french so i can't tell what exactly he wrote, but i understand c code and graphs 🙂

basically – he wrote c function that does reverse() of strings, and benchmarked it against pl/pgsql and pl/perl versions. of course c version is the fastest, but just take a look at how much faster it is. and how simple it is.

how many transactions per second?

i wanted to know how many transactions per second is my machine processing.

how to do so? a simple select to pg_stat_database will do the job (actually 2 selects 🙂

but since i have to write it anyway, perhaps i can/should make it so it will print the current value continuously?

and, while i'm at it, some kind of graph wouldn't be bad 🙂

Continue reading how many transactions per second?

better results paging in postgresql 8.2

some time ago merlin moncure wrote about one of new features of postgresql 8.2 – row-wise comparison.

i also read about it, but at first didn't find anything very useful about it – after all it doesn't give you any new functionality. any kind “(a, b, c) > (…)" can be written with standard column-based operators. so it's basically just a syntactic-sugar.

that's true. but merlin pointed me to not-so-obvious benefit – basically it allows much better paging of results. how? let's see.

Continue reading better results paging in postgresql 8.2

łosoś w sake [polish only]

ostatnio testowałem interesujący i dosyć prosty pomysł na jedzonko.

zaczęło się od tego, że przypadkiem usłyszałem w telewizji opis jakiejś potrawy: “to jest pieczona ryba (tu była jakaś nazwa, ale jej nie znam) marynowana w sake z syropem klonowym, zwróćcie uwagę na ten wytopiony tłuszcz – ryba musi był tłusta by się potrawa udała". i to było wszystko co usłyszałem. nie znałem proporcji, czasu, temperatury, nic.

ale – zawsze można poeksperymentować 🙂

Continue reading łosoś w sake [polish only]