On 6/5/2015 11:37 AM, Ravi Krishna wrote:
Why is PG even re-writing all rows when the data type is being changed from smaller (int) to larger (bigint) type, which automatically means existing data is safe. Like, changing from varchar(30) to varchar(50) should involve no rewrite of existing rows.
int to bigint requires storage change, as all bigints are 64 bit while all ints are 32 bit. it would be a MESS to try and keep track of a table that has some int and some bigint storage of a given field.
now, varchar 30 to 50, that I can't answer, are you sure that does a rewrite? the storage is exactly the same for those.
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