Merge pull request #42791 from RaduBerinde/backport19.2-42760

release-19.2: opt: fix incorrect lax key calculation

pkg/sql/opt/memo/testdata/logprops/index-join

@@ -55,7 +55,6 @@ SELECT y FROM a WHERE s = 'foo' AND x + y = 10
 ----
 project
  ├── columns: y:2(int)
- ├── lax-key: (2)
  ├── prune: (2)
  └── select
       ├── columns: x:1(int!null) y:2(int) s:3(string!null)

pkg/sql/opt/memo/testdata/logprops/scan

@@ -175,3 +175,32 @@ select
            └── lt [type=bool]
                 ├── variable: d [type=date]
                 └── const: '2017-01-05' [type=date]
+
+
+# Regression test for #42731: we were incorrectly setting cardinality [0 - 1].
+exec-ddl
+CREATE TABLE t42731 (id INT PRIMARY KEY, unique_value INT UNIQUE, notnull_value INT NOT NULL)
+----
+
+norm
+SELECT * FROM t42731 WHERE unique_value IS NULL AND notnull_value = 2000
+----
+select
+ ├── columns: id:1(int!null) unique_value:2(int) notnull_value:3(int!null)
+ ├── key: (1)
+ ├── fd: ()-->(2,3), (2)~~>(1)
+ ├── prune: (1)
+ ├── interesting orderings: (+1) (+2,+1)
+ ├── scan t42731
+ │    ├── columns: id:1(int!null) unique_value:2(int) notnull_value:3(int!null)
+ │    ├── key: (1)
+ │    ├── fd: (1)-->(2,3), (2)~~>(1,3)
+ │    ├── prune: (1-3)
+ │    └── interesting orderings: (+1) (+2,+1)
+ └── filters
+      ├── is [type=bool, outer=(2), constraints=(/2: [/NULL - /NULL]; tight), fd=()-->(2)]
+      │    ├── variable: unique_value [type=int]
+      │    └── null [type=unknown]
+      └── eq [type=bool, outer=(3), constraints=(/3: [/2000 - /2000]; tight), fd=()-->(3)]
+           ├── variable: notnull_value [type=int]
+           └── const: 2000 [type=int]

pkg/sql/opt/props/func_dep.go

@@ -1371,8 +1371,8 @@ func (f *FuncDepSet) inClosureOf(cols, in opt.ColSet, strict bool) bool {
 			if fd.from.SubsetOf(in) && !fd.to.SubsetOf(in) {
 				laxIn.UnionWith(fd.to)
 
-				// Equivalencies and constants are always transitive.
-				if fd.equiv || fd.from.Empty() {
+				// Equivalencies are always transitive.
+				if fd.equiv {
 					in.UnionWith(fd.to)
 
 					// Restart iteration to get transitive closure.

pkg/sql/opt/props/func_dep_test.go

@@ -46,7 +46,13 @@ func TestFuncDeps_ColsAreKey(t *testing.T) {
 		{cols: c(10), strict: false, lax: false},
 		{cols: c(11), strict: false, lax: false},
 		{cols: c(), strict: false, lax: false},
-		{cols: c(2, 11), strict: false, lax: true},
+
+		// This case is interesting: if we take into account that 3 is a constant,
+		// we could put 2 and 3 together and use (2,3)~~>(1,4,5) and (1)==(10) to
+		// prove that (2,3) is a lax key. But this is only true when that constant
+		// value for 3 is not NULL. We would have to pass non-null information to
+		// the check. See #42731.
+		{cols: c(2, 11), strict: false, lax: false},
 	}
 
 	for _, tc := range testcases {