Re[2]: [HACKERS] Fwd: Joins and links

Hello Tom,

Monday, July 05, 1999 you wrote:

T> If we did have such a concept, the speed penalties for supporting
T> hard links from one tuple to another would be enormous.  Every time
T> you change a tuple, you'd have to try to figure out what other tuples
T> reference it, and update them all.

I'm afraid that's mainly because fields in Postgres have variable
length and after update they go to the end of the table. Am I right?
In that case there could be done such referencing only with
tables with wixed width rows, whose updates can naturally be done
without moving. It is a little sacrifice, but it is worth it.

T> Finally, I'm not convinced that the results would be materially faster
T> than a standard mergejoin (assuming that you have indexes on both the
T> fields being joined) or hashjoin (in the case that one table is small
T> enough to be loaded into memory).

Consider this: no indices, no optimizer thinking, no index lookups -
no nothing! Just a sequential number of record multiplied by
record size. Exactly three CPU instructions: read, multiply,
lookup. Can you see the gain now?

Best regards, Leon