Add test framework for running Impala query tests via Python

This is the first set of changes required to start getting our functional test
infrastructure moved from JUnit to Python. After investigating a number of
option, I decided to go with a python test executor named py.test
(http://pytest.org/). It is very flexible, open source (MIT licensed), and will
enable us to do some cool things like parallel test execution.

As part of this change, we now use our "test vectors" for query test execution.
This will be very nice because it means if load the "core" dataset you know you
will be able to run the "core" query tests (specified by --exploration_strategy
when running the tests).

You will see that now each combination of table format + query exec options is
treated like an individual test case. this will make it much easier to debug
exactly where something failed.

These new tests can be run using the script at tests/run-tests.sh

testdata/workloads/functional-query/queries/QueryTest/insert_overwrite.test

@@ -1,3 +1,5 @@
+====
+---- QUERY
 # insert overwrite into unpartitioned table
 insert overwrite table insert_overwrite_nopart$TABLE 
 select int_col
@@ -8,6 +10,7 @@ RESET insert_overwrite_nopart$TABLE
 ---- PARTITIONS
 /: 10
 ====
+---- QUERY
 # Check results - note larger limit than expected in case there's more data written than there should be
 select col1 
 from insert_overwrite_nopart$TABLE 
@@ -27,6 +30,7 @@ int
 8
 9
 ====
+---- QUERY
 # Now do an overwrite that should delete what was just written
 insert overwrite table insert_overwrite_nopart$TABLE
 select 10
@@ -35,6 +39,7 @@ from tinyinttable
 ---- PARTITIONS
 /: 10
 ====
+---- QUERY
 # check results from previous insert
 select col1 
 from insert_overwrite_nopart$TABLE 
@@ -54,6 +59,7 @@ int
 10
 10
 ====
+---- QUERY
 # TODO: IMP-240 - Hive will delete data even for inserts that write nothing. When we fix IMP-240, this test should fail. 
 insert overwrite table insert_overwrite_nopart$TABLE
 select 3
@@ -62,23 +68,26 @@ limit 0
 ---- RESULTS
 ---- PARTITIONS
 ====
+---- QUERY
 select count(*) from insert_overwrite_nopart$TABLE
 ---- TYPES
 bigint
 ---- RESULTS
 10
 ====
+---- QUERY
 # Static partitioned insert
 insert overwrite table insert_overwrite_partitioned$TABLE
 PARTITION(col2=5)
 select int_col
 from tinyinttable
 ---- SETUP
-RESET insert_overwrite_partitioned$TABLE$TABLE
+RESET insert_overwrite_partitioned$TABLE
 ---- RESULTS
 ---- PARTITIONS
 /col2=5/: 10
 ====
+---- QUERY
 # Check results of previous insert
 select col1, col2 from insert_overwrite_partitioned$TABLE
 order by col1
@@ -97,6 +106,7 @@ int,int
 8,5
 9,5
 ====
+---- QUERY
 # Insert into another partition, to check that original partition stays intact
 insert overwrite table insert_overwrite_partitioned$TABLE
 PARTITION(col2=6)
@@ -108,6 +118,7 @@ RESET insert_overwrite_nopart$TABLE
 ---- PARTITIONS
 /col2=6/: 10
 ====
+---- QUERY
 # Check results of previous insert
 select col1, col2 from 
 insert_overwrite_partitioned$TABLE 
@@ -137,6 +148,7 @@ int,int
 8,6
 9,6
 ====
+---- QUERY
 # Overwrite one partition, check that the other partition remains intact
 insert overwrite table insert_overwrite_partitioned$TABLE
 partition(col2=5)
@@ -145,6 +157,7 @@ select 10 from tinyinttable
 ---- PARTITIONS
 /col2=5/: 10
 ====
+---- QUERY
 # Confirm that one partition is still intact
 select col1, col2 from insert_overwrite_partitioned$TABLE
 order by col2, col1 limit 30
@@ -172,6 +185,7 @@ int,int
 8,6
 9,6
 ====
+---- QUERY
 # Dynamic partitions
 insert overwrite table insert_overwrite_partitioned$TABLE
 partition(col2)
@@ -192,6 +206,7 @@ DROP PARTITIONS insert_overwrite_partitioned$TABLE
 /col2=8/: 1
 /col2=9/: 1
 ====
+---- QUERY
 # Confirm results of previous insert
 select col1, col2
 from insert_overwrite_partitioned$TABLE
@@ -211,6 +226,7 @@ int,int
 8,8
 9,9
 ====
+---- QUERY
 # Overwrite dynamic partition. Limit to 1 row without actually using limit, which forces non-parallel insert
 insert overwrite table insert_overwrite_partitioned$TABLE
 partition(col2)
@@ -220,6 +236,7 @@ where int_col = 0
 ---- PARTITIONS
 /col2=0/: 1
 ====
+---- QUERY
 select col1, col2
 from insert_overwrite_partitioned$TABLE
 order by col2
@@ -237,4 +254,4 @@ int,int
 7,7
 8,8
 9,9
-====
+====