I'm reloading data from Oracle database. It returns normally ca. 500k records. So with the transformations QV loads it for about an hour.
Today I started the reload at t, and after 0,5 hrs someone truncated the database table [so in the middle of the reload process].
My question is: if the QV started to process "SQL Select" part will I get all the data [500k]?
General question: does QV first executes the SQL SELECT and then stores all data from the query [how] and then transforms it or does it do it in parts [get 1 ->transform 1 ->get 2 -> transform 2 -> concatenate .....]?
the data came through complete so i assume that first the SQL SELECT is executed as a whole, if someone could confirm it would be nice.
I think this is Oracle database consistency mechanism. When you start select Oracle freezes all changes for your request. In your case Oracle created "copy" of truncated table.
Statement-Level Read Consistency block