"Pavan Deolasee" <[EMAIL PROTECTED]> writes: > On 9/12/07, Tom Lane <[EMAIL PROTECTED]> wrote: >> XXX the above being the case, why should we bother with all this extra >> mechanism? Seems we could dispense with "not ready for inserts".
> Without this additional step, while we are building the index in the first > phase > using a snapshot, its possible that a broken HOT chain may get created > forwarding to the tuple that we index. For example: > A table with two columns a and b. Say, we already have an index on 'a' > and creating a new index on 'b'. Say, there is a tuple (0, 1): (1, 11) in > the table where (0, 1) in the line pointer of the tuple. > This is the visible tuple when we took snapshot in the first phase and so > we shall index this tuple with key 11 and TID (0, 1). But before the first > phase > finishes, the tuple is updated to (0, 2): (1, 22). This would be a HOT > update > resulting in a broken chain. The root line pointer for the new tuple is > still (0, 1). Got it. I'll put something about this into the README. regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend