Tests: don't rely on the response of MEMORY USAGE when mem_allocator is not jemalloc (#10010)

It turns out that libc malloc can return an allocation of a different size on requests of the same size.
this means that matching MEMORY USAGE of one key to another copy of the same data can fail.

Solution:
Keep running the test that calls MEMORY USAGE, but ignore the response.
We do that by introducing a new utility function to get the memory usage, which always returns 1
when the allocator is not jemalloc.

Other changes:
Some formatting for datatype2.tcl

Co-authored-by: Oran Agra <oran@redislabs.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/tests/support/util.tcl b/tests/support/util.tcl
index d11841894..c4f90b29e 100644
--- a/tests/support/util.tcl
+++ b/tests/support/util.tcl
@@ -1002,3 +1002,13 @@ proc prepare_value {size} {
     }
     return $_v
 }
+
+proc memory_usage {key} {
+    set usage [r memory usage $key]
+    if {![string match {*jemalloc*} [s mem_allocator]]} {
+        # libc allocator can sometimes return a different size allocation for the same requested size
+        # this makes tests that rely on MEMORY USAGE unreliable, so instead we return a constant 1
+        set usage 1
+    }
+    return $usage
+}