Tom Lane schrieb am 18.04.2016 um 17:16:
For trigger, e.g. written in pl/pgsql, each sql command within the
function may see more new data beyond the (entry) snapshot of outer
command.
No it will not see "more data")
It runs in the same _transaction_ as the "firing" command and thus sees
**exactly** the same data as the triggering statement
No, that's not true: a trigger is a function and what it can see is
determined by the rules of the PL it's written in. Typically a
function that's marked STABLE or IMMUTABLE will see the same snapshot
as the calling query, but a function that's VOLATILE will take a new
snapshot for each query it contains.
Does that mean a VOLATILE function runs in a different transaction?
And does that mean it will see committed data that the calling statement would not see?
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