IMPALA-13188: Add test that compute stats does not result in a different tuple cache key

The patch introduces a new test, TestTupleCacheComputeStats, to
verify that compute stats does not change the tuple cache key.
The test creates a simple table with one row, runs an explain
on a basic query, then inserts more rows, computes the stats,
and reruns the same explain query. It compares the two results
to ensure that the cache keys are identical in the planning
phase.

Tests:
Passed the test.

Change-Id: I918232f0af3a6ab8c32823da4dba8f8cd31369d0
Reviewed-on: http://gerrit.cloudera.org:8080/21917
Reviewed-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com>
Tested-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com>

tests/util/parse_util.py

@@ -34,6 +34,7 @@ EXPECTED_TPCH_STRESS_QUERIES_COUNT = EXPECTED_TPCH_QUERIES_COUNT + 3
 MEM_ESTIMATE_PATTERN = re.compile(
     r"Per-Host Resource Estimates: Memory=(\d+\.?\d*)(P|T|G|M|K)?B")
 NEW_GLOG_ENTRY_PATTERN = re.compile(r"[IWEF](?P<Time>\d{4} \d{2}:\d{2}:\d{2}\.\d{6}).*")
+CACHE_KEY_PATTERN = re.compile(r"cache key: ([a-f0-9]+)")
 
 
 def parse_glog(text, start_time=None):
@@ -155,6 +156,31 @@ def match_memory_estimate(explain_lines):
   return mem_limit, units
 
 
+def match_cache_key(explain_lines):
+  """
+  Given a list of strings from EXPLAIN output, find the cache key.
+
+  Params:
+    explain_lines: list of str
+
+  Returns:
+    str - The cache key if found
+
+  Raises:
+    Exception if no cache key is found
+  """
+  cache_key = None
+  for line in explain_lines:
+    regex_result = CACHE_KEY_PATTERN.search(line)
+    if regex_result:
+      cache_key = regex_result.group(1)
+      break
+  if cache_key is None:
+    raise Exception(
+      'could not find cache key in explain string:\n' + '\n'.join(explain_lines))
+  return cache_key
+
+
 def get_bytes_summary_stats_counter(counter_name, runtime_profile):
   """Extracts a list of TSummaryStatsCounters from a given runtime profile where the units
      are in bytes. Each entry in the returned list corresponds to a single occurrence of