The first condition expressions we implemented in Alternator were the old
"Expected" syntax of conditional updates. That implementation had some
specific assumptions on how it handles errors: For example, in the "LT"
operator in "Expected", the second operand is always part of the query, so
an error in it (e.g., an unsupported type) resulted it a ValidationException
error.
When we implemented ConditionExpression and FilterExpression, we wrongly
used the same functions check_compare(), check_BETWEEN(), etc., to implement
them. This results in some inaccurate error handling. The worst example is
what happens when you use a FilterExpression with an expression such as
"x < y" - this filter is supposed to silently skip items whose "x" and "y"
attributes have unsupported or different types, but in our implementation
a bad type (e.g., a list) for y resulted in a ValidationException which
aborted the entire scan! Interestingly, in once case (that of BEGINS_WITH)
we actually noticed the slightly different behavior needed and implemented
the same operator twice - with ugly code duplication. But in other operators
we missed this problem completely.
This patch first adds extensive tests of how the different expressions
(Expected, QueryFilter, FilterExpression, ConditionExpression) and the
different operators handle various input errors - unsupported types,
missing items, incompatible types, etc. Importantly, the tests demonstrate
that there is often different behavior depending on whether the bad
input comes from the query, or from the item. Some of the new tests
fail before this patch, but others pass and were useful to verify that
the patch doesn't break anything that already worked correctly previously.
As usual, all the tests pass on Cassandra.
Finally, this patch *fixes* all these problems. The comparison functions
like check_compare() and check_BETWEEN() now not only take the operands,
they also take booleans saying if each of the operands came from the
query or from an item. The old-syntax caller (Expected or QueryFilter)
always say that the first operand is from the item and the second is
from the query - but in the new-syntax caller (ConditionExpression or
FilterExpression) any or all of the operands can come from the query
and need verification.
The old duplicated code for check_BEGINS_WITH() - which a TODO to remove
it - is finally removed. Instead we use the same idea of passing booleans
saying if each of its operands came from an item or from the query.
Fixes#8043
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
(cherry picked from commit 653610f4bc)
b47bdb053d