This patch ensures that setting the query option
enable_expr_rewrites=false will disable both constant folding in the
frontend (which it did already) and constant caching in the backend
(which is enabled in this patch). This gives a way for users to revert
to the old behaviour of non-deterministic UDFs before these
optimisations were added in Impala 2.8.
Before this patch, the backend would cache values based on IsConstant().
This meant that there was no way to override caching of values of
non-deterministic UDFs, e.g. with enable_expr_rewrites.
After this patch, we only cache literal values in the backend. This
offers the same performance as before in the common case where the
frontend will constant fold the expressions anyway.
Also rename some functions to more cleanly separate the backend concepts
of "constant" expressions and expressions that can be evaluated without
a TupleRow. In a future change (IMPALA-4617) we should remove the
IsConstant() analysis logic from the backend entirely and pass the
information from the frontend. We should also fix isConstant() in the
frontend so that it only returns true when it is safe to constant-fold
the expression (IMPALA-4606). Once that is done, we could revert back
to using IsConstant() instead of IsLiteral().
Testing:
Added targeted test to test constant folding of UDFs: we expect
different results depending on whether constant folding is enabled.
Also run TestUdfs with expr rewrites enabled and disabled, since this
can exercise different code paths. Refactored test_udfs somewhat to
avoid running uninteresting combinations of query options for
targeted tests and removed some 'drop * if not exists' statements
that aren't necessary when using unique_database.
This change revealed flakiness in test_mem_limit, which seems
to have only worked by coincidence. Updated TrackAllocation() to
actually set the query status when a memory limit is exceeded.
Looped this test for a while to make sure it isn't flaky any
more.
Also fix other test bugs where the vector argument is modified
in-place, which can leak out to other tests.
Change-Id: I0c76e3c8a8d92749256c312080ecd7aac5d99ce7
Reviewed-on: http://gerrit.cloudera.org:8080/5391
Reviewed-by: Tim Armstrong <tarmstrong@cloudera.com>
Tested-by: Impala Public Jenkins
This patch introduces the ability to specify a prepare and close
function for a UDF, as well as FunctionContext methods for maintaining
state across UDF invocations within a query. Many of the changes are
related to adding an Expr::Open() function which calls the UDF's
prepare function, if specified (it has to be called in Open() since
the LLVM module must be compiled first).
Change-Id: I581d90d03dff71f7ff5d4a6bef839ba6bc46b443
Reviewed-on: http://gerrit.ent.cloudera.com:8080/1693
Reviewed-by: Skye Wanderman-Milne <skye@cloudera.com>
Tested-by: jenkins
(cherry picked from commit 8e2ed7fb9051d98f89327715fdebd6f5ed22d6ee)
Reviewed-on: http://gerrit.ent.cloudera.com:8080/1757
