opt: fixup CTE stats on placeholder queries

During optbuilder phase we copy the initial expressions stats into the
fake-rel but this value can change when placeholders are assigned so add
a normalization step to do this so it happens on the assignplaceholder
path.

Fixes: cockroachdb#99389
Epic: none
Release note: none

pkg/sql/opt/norm/rules/with.opt

@@ -64,3 +64,14 @@
     )
     $private
 )
+
+# ReapplyBindingRowCount propagates stats changed after assign-placeholders.
+[ReapplyBindingRowCount, Normalize]
+(RecursiveCTE
+    $binding:*
+    $initial:* & (RowCountDifferent $binding $initial)
+    $recursive:*
+    $private:*
+)
+=>
+(ReapplyBindingRowCount $binding $initial $recursive $private)

pkg/sql/opt/norm/testdata/rules/with

@@ -3005,3 +3005,81 @@ project
  │              └── i:3 + 1 [as="?column?":4, outer=(3), immutable]
  └── projections
       └── i:2 [as=i:5, outer=(2)]
+
+exec-ddl
+CREATE TABLE yz (y INT, z INT, INDEX (y) STORING (z));
+----
+
+exec-ddl
+ALTER TABLE yz INJECT STATISTICS '[
+  {
+    "columns": ["y"],
+    "created_at": "2018-01-01 1:00:00.00000+00:00",
+    "row_count": 100000,
+    "distinct_count": 100000
+  },
+  {
+    "columns": ["z"],
+    "created_at": "2018-01-01 1:00:00.00000+00:00",
+    "row_count": 100000,
+    "distinct_count": 1
+  }
+]';
+----
+
+# Regression test for #99389.
+assign-placeholders-norm query-args=(1) format=show-stats
+WITH RECURSIVE cte(a,b) AS (
+  (SELECT * FROM yz WHERE y = $1)
+  UNION ALL
+  (SELECT y+1, z FROM yz LEFT JOIN cte ON b = z)
+)
+SELECT * FROM cte;
+----
+project
+ ├── columns: a:16 b:17
+ ├── immutable
+ ├── stats: [rows=10]
+ ├── recursive-c-t-e
+ │    ├── columns: a:6 b:7
+ │    ├── working table binding: &1
+ │    ├── initial columns: y:1 z:2
+ │    ├── recursive columns: "?column?":15 z:9
+ │    ├── immutable
+ │    ├── stats: [rows=10]
+ │    ├── fake-rel
+ │    │    ├── columns: a:6 b:7
+ │    │    ├── cardinality: [1 - ]
+ │    │    └── stats: [rows=1.00001, distinct(7)=0.100001, null(7)=0.0100001]
+ │    ├── select
+ │    │    ├── columns: y:1!null z:2
+ │    │    ├── stats: [rows=1.00001, distinct(1)=1, null(1)=0]
+ │    │    ├── fd: ()-->(1)
+ │    │    ├── scan yz
+ │    │    │    ├── columns: y:1 z:2
+ │    │    │    └── stats: [rows=100000, distinct(1)=100000, null(1)=0]
+ │    │    └── filters
+ │    │         └── y:1 = 1 [outer=(1), constraints=(/1: [/1 - /1]; tight), fd=()-->(1)]
+ │    └── project
+ │         ├── columns: "?column?":15 z:9
+ │         ├── immutable
+ │         ├── stats: [rows=100001]
+ │         ├── left-join (hash)
+ │         │    ├── columns: y:8 z:9 b:14
+ │         │    ├── stats: [rows=100001, distinct(14)=1, null(14)=0]
+ │         │    ├── scan yz
+ │         │    │    ├── columns: y:8 z:9
+ │         │    │    └── stats: [rows=100000, distinct(9)=1, null(9)=0]
+ │         │    ├── with-scan &1 (cte)
+ │         │    │    ├── columns: b:14
+ │         │    │    ├── mapping:
+ │         │    │    │    └──  b:7 => b:14
+ │         │    │    ├── cardinality: [1 - ]
+ │         │    │    └── stats: [rows=1.00001, distinct(14)=0.100001, null(14)=0.0100001]
+ │         │    └── filters
+ │         │         └── b:14 = z:9 [outer=(9,14), constraints=(/9: (/NULL - ]; /14: (/NULL - ]), fd=(9)==(14), (14)==(9)]
+ │         └── projections
+ │              └── y:8 + 1 [as="?column?":15, outer=(8), immutable]
+ └── projections
+      ├── a:6 [as=a:16, outer=(6)]
+      └── b:7 [as=b:17, outer=(7)]

pkg/sql/opt/norm/with_funcs.go

@@ -297,3 +297,46 @@ func (c *CustomFuncs) CanAddRecursiveLimit(
 func (c *CustomFuncs) GetRecursiveWithID(private *memo.RecursiveCTEPrivate) opt.WithID {
 	return private.WithID
 }
+
+func (c *CustomFuncs) ReapplyBindingRowCount(
+	binding, initial, recursive memo.RelExpr, private *memo.RecursiveCTEPrivate,
+) memo.RelExpr {
+	// The properties of the binding are tricky: the recursive expression is
+	// invoked repeatedly and these must hold each time. We can't use the initial
+	// expression's properties directly, as those only hold the first time the
+	// recursive query is executed. We don't really know the input row count,
+	// except for the first time we run the recursive query. We don't have
+	// anything better though.
+	card := initial.Relational().Cardinality.Union(recursive.Relational().Cardinality)
+	newRowCount := initial.Relational().Statistics().RowCount
+	newBinding := c.f.ConstructFakeRel(&memo.FakeRelPrivate{
+		Props: MakeBindingPropsForRecursiveCTE(card, binding.Relational().OutputCols, newRowCount),
+	})
+
+	// Re-optimize the recursive branch with the new properties.
+	withID := private.WithID
+	newWithID := c.f.Memo().NextWithID()
+	c.f.Metadata().AddWithBinding(newWithID, newBinding)
+	var replace ReplaceFunc
+	replace = func(e opt.Expr) opt.Expr {
+		if e == binding {
+			return newBinding
+		}
+		if withScan, ok := e.(*memo.WithScanExpr); ok && withScan.With == withID {
+			// Reconstruct the with scan using the new binding.
+			newPrivate := withScan.WithScanPrivate
+			newPrivate.With = newWithID
+			newPrivate.ID = c.f.Metadata().NextUniqueID()
+			return c.f.ConstructWithScan(&newPrivate)
+		}
+		return c.f.Replace(e, replace)
+	}
+	newRecursive := replace(recursive).(memo.RelExpr)
+	newPrivate := *private
+	newPrivate.WithID = newWithID
+	return c.f.ConstructRecursiveCTE(newBinding, initial, newRecursive, &newPrivate)
+}
+
+func (c *CustomFuncs) RowCountDifferent(binding, initial memo.RelExpr) bool {
+	return initial.Relational().Statistics().RowCount != binding.Relational().Statistics().RowCount
+}