opt: fix ordering-related optimizer panics

It is possible for some functional-dependency information to be visible
to a child operator but invisible to its parent. This could previously
cause panics when a child provided an ordering that could be proven to
satisfy the required ordering with the child FDs, but not with the
parent's FDs.

This patch adds a step to the logic that builds provided orderings that
ensures a provided ordering can be proven to respect the required ordering
without needing additional FD information. This ensures that a parent never
needs to know its child's FDs in order to prove that the provided ordering
is correct. The extra step is a no-op in the common case when the provided
ordering can already be proven to respect the required ordering.

Informs #85393
Informs #87806
Fixes #96288

Release note (bug fix): Fixed a rare internal error in the optimizer that has
existed since before version 22.1, which could occur while enforcing orderings
between SQL operators.

pkg/sql/opt/ordering/ordering.go

@@ -88,6 +88,7 @@ func BuildProvided(expr memo.RelExpr, required *props.OrderingChoice) opt.Orderi
 		return nil
 	}
 	provided := funcMap[expr.Op()].buildProvidedOrdering(expr, required)
+	provided = finalizeProvided(provided, required, expr.Relational().OutputCols)
 
 	if buildutil.CrdbTestBuild {
 		checkProvided(expr, required, provided)
@@ -423,6 +424,53 @@ func trimProvided(
 	return provided[:provIdx]
 }
 
+// finalizeProvided ensures that the provided ordering satisfies the following
+// properties:
+//  1. The provided ordering can be proven to satisfy the required ordering
+//     without the use of additional (e.g. functional dependency) information.
+//  2. The provided ordering is simplified, such that it does not contain any
+//     columns from the required ordering optional set.
+//  3. The provided ordering only refers to output columns for the operator.
+//
+// This step is necessary because it is possible for child operators to have
+// different functional dependency information than their parents as well as
+// different output columns. We have to protect against the case where a parent
+// operator cannot prove that its child's provided ordering satisfies its
+// required ordering.
+func finalizeProvided(
+	provided opt.Ordering, required *props.OrderingChoice, outCols opt.ColSet,
+) (newProvided opt.Ordering) {
+	// First check if the given provided is already suitable.
+	providedCols := provided.ColSet()
+	if len(provided) == len(required.Columns) && providedCols.SubsetOf(outCols) {
+		needsRemap := false
+		for i := range provided {
+			choice, ordCol := required.Columns[i], provided[i]
+			if !choice.Group.Contains(ordCol.ID()) || choice.Descending != ordCol.Descending() {
+				needsRemap = true
+				break
+			}
+		}
+		if !needsRemap {
+			return provided
+		}
+	}
+	newProvided = make(opt.Ordering, len(required.Columns))
+	for i, choice := range required.Columns {
+		group := choice.Group.Intersection(outCols)
+		if group.Intersects(providedCols) {
+			// Prefer using columns from the provided ordering if possible.
+			group.IntersectionWith(providedCols)
+		}
+		col, ok := group.Next(0)
+		if !ok {
+			panic(errors.AssertionFailedf("no output column equivalent to %d", redact.Safe(col)))
+		}
+		newProvided[i] = opt.MakeOrderingColumn(col, choice.Descending)
+	}
+	return newProvided
+}
+
 // checkRequired runs sanity checks on the ordering required of an operator.
 func checkRequired(expr memo.RelExpr, required *props.OrderingChoice) {
 	rel := expr.Relational()
@@ -472,12 +520,4 @@ func checkProvided(expr memo.RelExpr, required *props.OrderingChoice, provided o
 			))
 		}
 	}
-
-	// The provided ordering should not have unnecessary columns.
-	fds := &expr.Relational().FuncDeps
-	if trimmed := trimProvided(provided, required, fds); len(trimmed) != len(provided) {
-		panic(errors.AssertionFailedf(
-			"provided %s can be trimmed to %s (FDs: %s)", redact.Safe(provided), redact.Safe(trimmed), redact.Safe(fds),
-		))
-	}
 }

pkg/sql/opt/xform/testdata/physprops/ordering

@@ -3072,7 +3072,7 @@ sort
  ├── cardinality: [0 - 0]
  ├── key: ()
  ├── fd: ()-->(6,12,23)
- ├── ordering: +(12|23),-6 [actual: ]
+ ├── ordering: +(12|23),-6 [actual: +12,-6]
  └── values
       ├── columns: tab_922.crdb_internal_mvcc_timestamp:6!null col1_4:12!null col_2150:23!null
       ├── cardinality: [0 - 0]
@@ -3097,16 +3097,51 @@ distinct-on
  │    ├── columns: c1:1!null c2:2
  │    ├── key: (1)
  │    ├── fd: (1)-->(2)
- │    ├── ordering: +1 [actual: +2,+1]
+ │    ├── ordering: +1
  │    ├── scan v0@i3
  │    │    ├── columns: c1:5!null c2:6
  │    │    ├── constraint: /6/5: [/'2023-01-31 00:00:00' - /'2023-01-31 00:00:00']
  │    │    ├── key: (5)
  │    │    ├── fd: (5)-->(6)
- │    │    └── ordering: +5 [actual: +6,+5]
+ │    │    └── ordering: +5
  │    └── projections
  │         ├── c1:5 [as=c1:1, outer=(5)]
  │         └── c2:6 [as=c2:2, outer=(6)]
  └── aggregations
       └── const-agg [as=c2:2, outer=(2)]
            └── c2:2
+
+opt
+SELECT c1 FROM v0
+WHERE (c1 = c1 AND c2 = '01-31-2023 00:00:00'::TIMESTAMP)
+  OR (c1 = b'00' AND c1 = b'0')
+  OR (c1 IS NULL AND c2 IS NULL)
+ORDER BY c1;
+----
+project
+ ├── columns: c1:1!null
+ ├── key: (1)
+ ├── ordering: +1
+ └── distinct-on
+      ├── columns: c1:1!null c2:2
+      ├── grouping columns: c1:1!null
+      ├── key: (1)
+      ├── fd: (1)-->(2)
+      ├── ordering: +1
+      ├── project
+      │    ├── columns: c1:1!null c2:2
+      │    ├── key: (1)
+      │    ├── fd: (1)-->(2)
+      │    ├── ordering: +1
+      │    ├── scan v0@i3
+      │    │    ├── columns: c1:5!null c2:6
+      │    │    ├── constraint: /6/5: [/'2023-01-31 00:00:00' - /'2023-01-31 00:00:00']
+      │    │    ├── key: (5)
+      │    │    ├── fd: (5)-->(6)
+      │    │    └── ordering: +5
+      │    └── projections
+      │         ├── c1:5 [as=c1:1, outer=(5)]
+      │         └── c2:6 [as=c2:2, outer=(6)]
+      └── aggregations
+           └── const-agg [as=c2:2, outer=(2)]
+                └── c2:2

pkg/sql/opt/xform/testdata/rules/join

@@ -9823,7 +9823,7 @@ project
       │         ├── cardinality: [0 - 1]
       │         ├── key: (25)
       │         ├── fd: (25)-->(26,27), (27)~~>(25,26)
-      │         ├── ordering: +25 [actual: ]
+      │         ├── ordering: +25
       │         └── project
       │              ├── columns: a:25!null b:26!null c:27!null q:31!null r:32!null
       │              ├── cardinality: [0 - 1]