[SPARK-24381][TESTING] Add unit tests for NOT IN subquery around null…

… values

## What changes were proposed in this pull request?
This PR adds several unit tests along the `cols NOT IN (subquery)` pathway. There are a scattering of tests here and there which cover this codepath, but there doesn't seem to be a unified unit test of the correctness of null-aware anti joins anywhere. I have also added a brief explanation of how this expression behaves in SubquerySuite. Lastly, I made some clarifying changes in the NOT IN pathway in RewritePredicateSubquery.

## How was this patch tested?
Added unit tests! There should be no behavioral change in this PR.

Author: Miles Yucht <[email protected]>

Closes #21425 from mgyucht/spark-24381.

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/subquery.scala

@@ -116,15 +116,16 @@ object RewritePredicateSubquery extends Rule[LogicalPlan] with PredicateHelper {
           //   (a1,a2,...) = (b1,b2,...)
           // to
           //   (a1=b1 OR isnull(a1=b1)) AND (a2=b2 OR isnull(a2=b2)) AND ...
-          val joinConds = splitConjunctivePredicates(joinCond.get)
+          val baseJoinConds = splitConjunctivePredicates(joinCond.get)
+          val nullAwareJoinConds = baseJoinConds.map(c => Or(c, IsNull(c)))
           // After that, add back the correlated join predicate(s) in the subquery
           // Example:
           // SELECT ... FROM A WHERE A.A1 NOT IN (SELECT B.B1 FROM B WHERE B.B2 = A.A2 AND B.B3 > 1)
           // will have the final conditions in the LEFT ANTI as
-          // (A.A1 = B.B1 OR ISNULL(A.A1 = B.B1)) AND (B.B2 = A.A2)
-          val pairs = (joinConds.map(c => Or(c, IsNull(c))) ++ conditions).reduceLeft(And)
+          // (A.A1 = B.B1 OR ISNULL(A.A1 = B.B1)) AND (B.B2 = A.A2) AND B.B3 > 1
+          val finalJoinCond = (nullAwareJoinConds ++ conditions).reduceLeft(And)
           // Deduplicate conflicting attributes if any.
-          dedupJoin(Join(outerPlan, sub, LeftAnti, Option(pairs)))
+          dedupJoin(Join(outerPlan, sub, LeftAnti, Option(finalJoinCond)))
         case (p, predicate) =>
           val (newCond, inputPlan) = rewriteExistentialExpr(Seq(predicate), p)
           Project(p.output, Filter(newCond.get, inputPlan))

sql/core/src/test/resources/sql-tests/inputs/subquery/in-subquery/not-in-unit-tests-multi-column-literal.sql

@@ -0,0 +1,39 @@
+-- Unit tests for simple NOT IN predicate subquery across multiple columns.
+--
+-- See not-in-single-column-unit-tests.sql for an introduction.
+-- This file has the same test cases as not-in-unit-tests-multi-column.sql with literals instead of
+-- subqueries. Small changes have been made to the literals to make them typecheck.
+
+CREATE TEMPORARY VIEW m AS SELECT * FROM VALUES
+  (null, null),
+  (null, 1.0),
+  (2, 3.0),
+  (4, 5.0)
+  AS m(a, b);
+
+-- Case 1 (not possible to write a literal with no rows, so we ignore it.)
+-- (subquery is empty -> row is returned)
+
+-- Cases 2, 3 and 4 are currently broken, so I have commented them out here.
+-- Filed https://issues.apache.org/jira/browse/SPARK-24395 to fix and restore these test cases.
+
+  -- Case 5
+  -- (one null column with no match -> row is returned)
+SELECT *
+FROM   m
+WHERE  b = 1.0 -- Matches (null, 1.0)
+       AND (a, b) NOT IN ((2, 3.0));
+
+  -- Case 6
+  -- (no null columns with match -> row not returned)
+SELECT *
+FROM   m
+WHERE  b = 3.0 -- Matches (2, 3.0)
+       AND (a, b) NOT IN ((2, 3.0));
+
+  -- Case 7
+  -- (no null columns with no match -> row is returned)
+SELECT *
+FROM   m
+WHERE  b = 5.0 -- Matches (4, 5.0)
+       AND (a, b) NOT IN ((2, 3.0));

sql/core/src/test/resources/sql-tests/inputs/subquery/in-subquery/not-in-unit-tests-multi-column.sql

@@ -0,0 +1,98 @@
+-- Unit tests for simple NOT IN predicate subquery across multiple columns.
+--
+-- See not-in-single-column-unit-tests.sql for an introduction.
+--
+-- Test cases for multi-column ``WHERE a NOT IN (SELECT c FROM r ...)'':
+-- | # | does subquery include null?     | do filter columns contain null? | a = c? | b = d? | row included in result? |
+-- | 1 | empty                           | *                               | *      | *      | yes                     |
+-- | 2 | 1+ row has null for all columns | *                               | *      | *      | no                      |
+-- | 3 | no row has null for all columns | (yes, yes)                      | *      | *      | no                      |
+-- | 4 | no row has null for all columns | (no, yes)                       | yes    | *      | no                      |
+-- | 5 | no row has null for all columns | (no, yes)                       | no     | *      | yes                     |
+-- | 6 | no                              | (no, no)                        | yes    | yes    | no                      |
+-- | 7 | no                              | (no, no)                        | _      | _      | yes                     |
+--
+-- This can be generalized to include more tests for more columns, but it covers the main cases
+-- when there is more than one column.
+
+CREATE TEMPORARY VIEW m AS SELECT * FROM VALUES
+  (null, null),
+  (null, 1.0),
+  (2, 3.0),
+  (4, 5.0)
+  AS m(a, b);
+
+CREATE TEMPORARY VIEW s AS SELECT * FROM VALUES
+  (null, null),
+  (0, 1.0),
+  (2, 3.0),
+  (4, null)
+  AS s(c, d);
+
+  -- Case 1
+  -- (subquery is empty -> row is returned)
+SELECT *
+FROM   m
+WHERE  (a, b) NOT IN (SELECT *
+                      FROM   s
+                      WHERE  d > 5.0) -- Matches no rows
+;
+
+  -- Case 2
+  -- (subquery contains a row with null in all columns -> row not returned)
+SELECT *
+FROM   m
+WHERE  (a, b) NOT IN (SELECT *
+                      FROM s
+                      WHERE c IS NULL AND d IS NULL) -- Matches only (null, null)
+;
+
+  -- Case 3
+  -- (probe-side columns are all null -> row not returned)
+SELECT *
+FROM   m
+WHERE  a IS NULL AND b IS NULL -- Matches only (null, null)
+       AND (a, b) NOT IN (SELECT *
+                          FROM s
+                          WHERE c IS NOT NULL) -- Matches (0, 1.0), (2, 3.0), (4, null)
+;
+
+  -- Case 4
+  -- (one column null, other column matches a row in the subquery result -> row not returned)
+SELECT *
+FROM   m
+WHERE  b = 1.0 -- Matches (null, 1.0)
+       AND (a, b) NOT IN (SELECT *
+                          FROM s
+                          WHERE c IS NOT NULL) -- Matches (0, 1.0), (2, 3.0), (4, null)
+;
+
+  -- Case 5
+  -- (one null column with no match -> row is returned)
+SELECT *
+FROM   m
+WHERE  b = 1.0 -- Matches (null, 1.0)
+       AND (a, b) NOT IN (SELECT *
+                          FROM s
+                          WHERE c = 2) -- Matches (2, 3.0)
+;
+
+  -- Case 6
+  -- (no null columns with match -> row not returned)
+SELECT *
+FROM   m
+WHERE  b = 3.0 -- Matches (2, 3.0)
+       AND (a, b) NOT IN (SELECT *
+                          FROM s
+                          WHERE c = 2) -- Matches (2, 3.0)
+;
+
+  -- Case 7
+  -- (no null columns with no match -> row is returned)
+SELECT *
+FROM   m
+WHERE  b = 5.0 -- Matches (4, 5.0)
+       AND (a, b) NOT IN (SELECT *
+                          FROM s
+                          WHERE c = 2) -- Matches (2, 3.0)
+;

sql/core/src/test/resources/sql-tests/inputs/subquery/in-subquery/not-in-unit-tests-single-column-literal.sql

@@ -0,0 +1,42 @@
+-- Unit tests for simple NOT IN with a literal expression of a single column
+--
+-- More information can be found in not-in-unit-tests-single-column.sql.
+-- This file has the same test cases as not-in-unit-tests-single-column.sql with literals instead of
+-- subqueries.
+
+CREATE TEMPORARY VIEW m AS SELECT * FROM VALUES
+  (null, 1.0),
+  (2, 3.0),
+  (4, 5.0)
+  AS m(a, b);
+
+  -- Uncorrelated NOT IN Subquery test cases
+  -- Case 1 (not possible to write a literal with no rows, so we ignore it.)
+  -- (empty subquery -> all rows returned)
+
+  -- Case 2
+  -- (subquery includes null -> no rows returned)
+SELECT *
+FROM   m
+WHERE  a NOT IN (null);
+
+  -- Case 3
+  -- (probe column is null -> row not returned)
+SELECT *
+FROM   m
+WHERE  b = 1.0 -- Only matches (null, 1.0)
+       AND a NOT IN (2);
+
+  -- Case 4
+  -- (probe column matches subquery row -> row not returned)
+SELECT *
+FROM   m
+WHERE  b = 3.0 -- Only matches (2, 3.0)
+       AND a NOT IN (2);
+
+  -- Case 5
+  -- (probe column does not match subquery row -> row is returned)
+SELECT *
+FROM   m
+WHERE  b = 3.0 -- Only matches (2, 3.0)
+       AND a NOT IN (6);

sql/core/src/test/resources/sql-tests/inputs/subquery/in-subquery/not-in-unit-tests-single-column.sql

@@ -0,0 +1,123 @@
+-- Unit tests for simple NOT IN predicate subquery across a single column.
+--
+-- ``col NOT IN expr'' is quite difficult to reason about. There are many edge cases, some of the
+-- rules are confusing to the uninitiated, and precedence and treatment of null values is plain
+-- unintuitive. To make this simpler to understand, I've come up with a plain English way of
+-- describing the expected behavior of this query.
+--
+-- - If the subquery is empty (i.e. returns no rows), the row should be returned, regardless of
+--   whether the filtered columns include nulls.
+-- - If the subquery contains a result with all columns null, then the row should not be returned.
+-- - If for all non-null filter columns there exists a row in the subquery in which each column
+--   either
+--   1. is equal to the corresponding filter column or
+--   2. is null
+--   then the row should not be returned. (This includes the case where all filter columns are
+--   null.)
+-- - Otherwise, the row should be returned.
+--
+-- Using these rules, we can come up with a set of test cases for single-column and multi-column
+-- NOT IN test cases.
+--
+-- Test cases for single-column ``WHERE a NOT IN (SELECT c FROM r ...)'':
+-- | # | does subquery include null? | is a null? | a = c? | row with a included in result? |
+-- | 1 | empty                       |            |        | yes                            |
+-- | 2 | yes                         |            |        | no                             |
+-- | 3 | no                          | yes        |        | no                             |
+-- | 4 | no                          | no         | yes    | no                             |
+-- | 5 | no                          | no         | no     | yes                            |
+--
+-- There are also some considerations around correlated subqueries. Correlated subqueries can
+-- cause cases 2, 3, or 4 to be reduced to case 1 by limiting the number of rows returned by the
+-- subquery, so the row from the parent table should always be included in the output.
+
+CREATE TEMPORARY VIEW m AS SELECT * FROM VALUES
+  (null, 1.0),
+  (2, 3.0),
+  (4, 5.0)
+  AS m(a, b);
+
+CREATE TEMPORARY VIEW s AS SELECT * FROM VALUES
+  (null, 1.0),
+  (2, 3.0),
+  (6, 7.0)
+  AS s(c, d);
+
+  -- Uncorrelated NOT IN Subquery test cases
+  -- Case 1
+  -- (empty subquery -> all rows returned)
+SELECT *
+FROM   m
+WHERE  a NOT IN (SELECT c
+                 FROM   s
+                 WHERE  d > 10.0) -- (empty subquery)
+;
+
+  -- Case 2
+  -- (subquery includes null -> no rows returned)
+SELECT *
+FROM   m
+WHERE  a NOT IN (SELECT c
+                 FROM   s
+                 WHERE  d = 1.0) -- Only matches (null, 1.0)
+;
+
+  -- Case 3
+  -- (probe column is null -> row not returned)
+SELECT *
+FROM   m
+WHERE  b = 1.0 -- Only matches (null, 1.0)
+       AND a NOT IN (SELECT c
+                     FROM   s
+                     WHERE  d = 3.0) -- Matches (2, 3.0)
+;
+
+  -- Case 4
+  -- (probe column matches subquery row -> row not returned)
+SELECT *
+FROM   m
+WHERE  b = 3.0 -- Only matches (2, 3.0)
+       AND a NOT IN (SELECT c
+                     FROM   s
+                     WHERE  d = 3.0) -- Matches (2, 3.0)
+;
+
+  -- Case 5
+  -- (probe column does not match subquery row -> row is returned)
+SELECT *
+FROM   m
+WHERE  b = 3.0 -- Only matches (2, 3.0)
+       AND a NOT IN (SELECT c
+                     FROM   s
+                     WHERE  d = 7.0) -- Matches (6, 7.0)
+;
+
+  -- Correlated NOT IN subquery test cases
+  -- Case 2->1
+  -- (subquery had nulls but they are removed by correlated subquery -> all rows returned)
+SELECT *
+FROM   m
+WHERE a NOT IN (SELECT c
+                FROM   s
+                WHERE  d = b + 10) -- Matches no row
+;
+
+  -- Case 3->1
+  -- (probe column is null but subquery returns no rows -> row is returned)
+SELECT *
+FROM   m
+WHERE  b = 1.0 -- Only matches (null, 1.0)
+       AND a NOT IN (SELECT c
+                     FROM   s
+                     WHERE  d = b + 10) -- Matches no row
+;
+
+  -- Case 4->1
+  -- (probe column matches row which is filtered out by correlated subquery -> row is returned)
+SELECT *
+FROM   m
+WHERE  b = 3.0 -- Only matches (2, 3.0)
+       AND a NOT IN (SELECT c
+                     FROM   s
+                     WHERE  d = b + 10) -- Matches no row
+;

sql/core/src/test/resources/sql-tests/results/subquery/in-subquery/not-in-unit-tests-multi-column-literal.sql.out

@@ -0,0 +1,54 @@
+-- Automatically generated by SQLQueryTestSuite
+-- Number of queries: 4
+
+
+-- !query 0
+CREATE TEMPORARY VIEW m AS SELECT * FROM VALUES
+  (null, null),
+  (null, 1.0),
+  (2, 3.0),
+  (4, 5.0)
+  AS m(a, b)
+-- !query 0 schema
+struct<>
+-- !query 0 output
+
+
+
+-- !query 1
+-- Case 5
+  -- (one null column with no match -> row is returned)
+SELECT *
+FROM   m
+WHERE  b = 1.0 -- Matches (null, 1.0)
+       AND (a, b) NOT IN ((2, 3.0))
+-- !query 1 schema
+struct<a:int,b:decimal(2,1)>
+-- !query 1 output
+NULL	1
+
+
+-- !query 2
+-- Case 6
+  -- (no null columns with match -> row not returned)
+SELECT *
+FROM   m
+WHERE  b = 3.0 -- Matches (2, 3.0)
+       AND (a, b) NOT IN ((2, 3.0))
+-- !query 2 schema
+struct<a:int,b:decimal(2,1)>
+-- !query 2 output
+
+
+
+-- !query 3
+-- Case 7
+  -- (no null columns with no match -> row is returned)
+SELECT *
+FROM   m
+WHERE  b = 5.0 -- Matches (4, 5.0)
+       AND (a, b) NOT IN ((2, 3.0))
+-- !query 3 schema
+struct<a:int,b:decimal(2,1)>
+-- !query 3 output
+4	5