> why does ALTER TABLE ADD new_col int default 0 rebuilds
> existing indexes ?
Because it has to rewrite the whole table to insert the default value
in every row. A REINDEX is way more efficient for recovering from that
than any row-by-row update would be.
thanks for explaining.
>> I wonder whether we need to do something to actively prevent functions
>> used in an index from querying the database? It's not too hard to
>> imagine crashing the backend by playing this sort of game.
> the game was seemingly fulfilling a requirement. dunno what
> i should be doing now.
It sorta looks to me like you're trying to get the effect of a
materialized view --- have you looked at the techdocs pages about
how to do those in Postgres?
We map the URL to category_id .
if someone requests URL SPORTS_AND_ENTERTAINMENT/SPORT_PRODUCTS/CAR_RACING
we server the data in category_id 641 thats why the functional
index is required. You suggesting to create a mat view for this lookup ?
Actually there is no *real* issue we seldom add columns to that
table. I might as well leave the system like this and REINDEX the table
after i do something that possibly corrupts the functional index.
SELECT category_id , upper(general.cat_url(category_id)) from
general.web_category_master limit 10;
category_id upper
----------- ------------------------------------------------------------
641 SPORTS_AND_ENTERTAINMENT/SPORT_PRODUCTS/CAR_RACING
1407 SECURITY_AND_PROTECTION/SECURITY_EQUIPMENT
1065 MINERAL_AND_METALS/MINERALS_AND_REFRACTORIES
474 HEALTH_AND_BEAUTY/PERSONAL_CARE/OTHERS
561 OFFICE_SUPPLIES/OTHERS
277 CONSTRUCTION_AND_REAL_ESTATE/REAL_ESTATE/SHOPS
1017 INDUSTRIAL_SUPPLIES/INDUSTRIAL_BRAKES_AND_CLUTCHES
580 OFFICE_SUPPLIES/PHOTOGRAPHY_AND_OPTICS/TIME_RECORDING
836 CHEMICALS/FINE_CHEMICALS_ALL
i think i should also change the function type to STABLE instead of
IMMUTABLE . (it does not have impact on this issue though)
Regds
mallah.
regards, tom lane
