[IMPALA-91] Make EXPLAIN output easier to interpret

• Type: Task
• Status: Resolved
• Priority: Blocker
• Resolution: Fixed
• Affects Version/s: Impala 0.5
• Fix Version/s: Impala 1.0
• Assignee: Alan Choi
• Reporter: Lenni Kuff
• Created: 22/Feb/13 15:30
• Updated: 20/Dec/15 00:04
• Resolved: 24/Apr/13 21:52

Description

To make it easier to interpret, for a query like:

select *
from alltypesagg a
full outer join alltypessmall b using (id, int_col)
right join alltypesaggnonulls c on (a.id = c.id and b.string_col = c.string_col)
where a.day >= 6
and b.month > 2
and c.day < 3
and a.tinyint_col = 15
and b.string_col = '15'
and a.tinyint_col + b.tinyint_col < 15
and a.float_col - c.double_col < 0
and (b.double_col * c.tinyint_col > 1000 or c.tinyint_col < 1000)

the output in verbose mode could look like
HASH JOIN
JOIN OP: RIGHT OUTER JOIN
HASH PREDICATES: a.id = c.id, b.string_col = c.string_col
OTHER PREDICATES: a.float_col - c.double_col < 0.0, b.double_col *
c.tinyint_col > 1000.0 OR c.tinyint_col < 1000
TUPLE IDS: 0N 1N 2
INNER:
SCAN HDFS table=default.alltypesaggnonulls (3) compact
TUPLE IDS: 2
HASH JOIN
JOIN OP: FULL OUTER JOIN
HASH PREDICATES: a.id = b.id, a.int_col = b.int_col
OTHER PREDICATES: a.tinyint_col + b.tinyint_col < 15
TUPLE IDS: 0N 1N
INNER:
SCAN HDFS table=default.alltypessmall (1) compact
PREDICATES: b.string_col = '15'
TUPLE IDS: 1
SCAN HDFS table=default.alltypesagg (0)
PREDICATES: a.tinyint_col = 15
TUPLE IDS: 0


right now it is:

HASH JOIN
JOIN OP: RIGHT OUTER JOIN
HASH PREDICATES:
a.id = c.id
b.string_col = c.string_col
OTHER PREDICATES: a.float_col - c.double_col < 0.0, b.double_col *
c.tinyint_col > 1000.0 OR c.tinyint_col < 1000
TUPLE IDS: 0N 1N 2
HASH JOIN
JOIN OP: FULL OUTER JOIN
HASH PREDICATES:
a.id = b.id
a.int_col = b.int_col
OTHER PREDICATES: a.tinyint_col + b.tinyint_col < 15
TUPLE IDS: 0N 1N
SCAN HDFS table=default.alltypesagg (0)
PREDICATES: a.tinyint_col = 15
TUPLE IDS: 0
SCAN HDFS table=default.alltypessmall (1) compact
PREDICATES: b.string_col = '15'
TUPLE IDS: 1
SCAN HDFS table=default.alltypesaggnonulls (3) compact
TUPLE IDS: 2


in regular mode, it could be something like
HASH JOIN
JOIN OP: RIGHT OUTER JOIN
INNER:
SCAN HDFS table=default.alltypesaggnonulls
HASH JOIN
JOIN OP: FULL OUTER JOIN
INNER:
SCAN HDFS table=default.alltypessmall
SCAN HDFS table=default.alltypesagg (0)

Sub-Tasks

• Plans should explicitly mention the join strategy: Resolved