sql: add tests for tail-call property

This commit adds tests for the `ExtractTailCalls` function from the
previous commit, and adds a `tail-call` field to `UDFCall` expressions
that are in tail-call position in another routine. It also adds a
regression test for cockroachdb#120916.

Informs cockroachdb#120916

Release note: None

pkg/ccl/logictestccl/testdata/logic_test/explain_call_plpgsql

@@ -85,6 +85,7 @@ call
                 ├── fd: ()-->(5)
                 └── tuple [type=tuple{void}]
                      └── udf: _stmt_raise_1 [type=void]
+                          ├── tail-call
                           ├── args
                           │    └── variable: x:1 [type=int]
                           ├── params: x:2(int)

pkg/ccl/logictestccl/testdata/logic_test/nested_routines

@@ -0,0 +1,27 @@
+# LogicTest: !local-mixed-23.1 !local-mixed-23.2
+
+# Regression test for #120916 - the nested routine is not in tail-call position,
+# and so cannot be a target for TCO.
+statement ok
+CREATE FUNCTION f_nested(x INT) RETURNS INT AS $$
+  BEGIN
+    x := x * 2;
+    RETURN x;
+  END
+$$ LANGUAGE PLpgSQL;
+
+statement ok
+CREATE FUNCTION f() RETURNS RECORD AS $$
+  DECLARE
+    a INT := -2;
+  BEGIN
+    a := f_nested(a);
+    RAISE NOTICE 'here';
+    RETURN (a, -a);
+  END
+$$ LANGUAGE PLpgSQL;
+
+query II
+SELECT * FROM f() AS g(x INT, y INT);
+----
+-4  4

pkg/ccl/logictestccl/tests/fakedist-disk/BUILD.bazel

@@ -12,7 +12,7 @@ go_test(
         "//build/toolchains:is_heavy": {"test.Pool": "heavy"},
         "//conditions:default": {"test.Pool": "large"},
     }),
-    shard_count = 26,
+    shard_count = 27,
     tags = [
         "ccl_test",
         "cpu:2",

pkg/ccl/logictestccl/tests/fakedist-vec-off/BUILD.bazel

@@ -12,7 +12,7 @@ go_test(
         "//build/toolchains:is_heavy": {"test.Pool": "heavy"},
         "//conditions:default": {"test.Pool": "large"},
     }),
-    shard_count = 26,
+    shard_count = 27,
     tags = [
         "ccl_test",
         "cpu:2",

pkg/ccl/logictestccl/tests/fakedist/BUILD.bazel

@@ -12,7 +12,7 @@ go_test(
         "//build/toolchains:is_heavy": {"test.Pool": "heavy"},
         "//conditions:default": {"test.Pool": "large"},
     }),
-    shard_count = 27,
+    shard_count = 28,
     tags = [
         "ccl_test",
         "cpu:2",

pkg/ccl/logictestccl/tests/local-legacy-schema-changer/BUILD.bazel

@@ -9,7 +9,7 @@ go_test(
         "//pkg/ccl/logictestccl:testdata",  # keep
     ],
     exec_properties = {"test.Pool": "large"},
-    shard_count = 26,
+    shard_count = 27,
     tags = [
         "ccl_test",
         "cpu:1",

pkg/ccl/logictestccl/tests/local-read-committed/BUILD.bazel

@@ -10,7 +10,7 @@ go_test(
         "//pkg/sql/opt/exec/execbuilder:testdata",  # keep
     ],
     exec_properties = {"test.Pool": "large"},
-    shard_count = 33,
+    shard_count = 34,
     tags = [
         "ccl_test",
         "cpu:1",

pkg/ccl/logictestccl/tests/local-vec-off/BUILD.bazel

@@ -9,7 +9,7 @@ go_test(
         "//pkg/ccl/logictestccl:testdata",  # keep
     ],
     exec_properties = {"test.Pool": "large"},
-    shard_count = 26,
+    shard_count = 27,
     tags = [
         "ccl_test",
         "cpu:1",

pkg/ccl/logictestccl/tests/local/BUILD.bazel

@@ -9,7 +9,7 @@ go_test(
         "//pkg/ccl/logictestccl:testdata",  # keep
     ],
     exec_properties = {"test.Pool": "large"},
-    shard_count = 42,
+    shard_count = 43,
     tags = [
         "ccl_test",
         "cpu:1",

pkg/sql/opt/memo/expr_format.go

@@ -171,6 +171,10 @@ type ExprFmtCtx struct {
 	// seenUDFs is used to ensure that formatting of recursive UDFs does not
 	// infinitely recurse.
 	seenUDFs map[*UDFDefinition]struct{}
+
+	// tailCalls allows for quick lookup of all the routines in tail-call position
+	// when the last body statement of a routine is formatted.
+	tailCalls map[*UDFCallExpr]struct{}
 }
 
 // makeExprFmtCtxForString creates an expression formatting context from a new
@@ -957,13 +961,18 @@ func (f *ExprFmtCtx) formatScalarWithLabel(
 			}
 			n := tp.Child("body")
 			for i := range def.Body {
+				stmtNode := n
 				if i == 0 && def.CursorDeclaration != nil {
 					// The first statement is opening a cursor.
-					cur := n.Child("open-cursor")
-					f.formatExpr(def.Body[i], cur)
-					continue
+					stmtNode = n.Child("open-cursor")
+				}
+				prevTailCalls := f.tailCalls
+				if i == len(def.Body)-1 {
+					f.tailCalls = make(map[*UDFCallExpr]struct{})
+					ExtractTailCalls(def.Body[i], f.tailCalls)
 				}
-				f.formatExpr(def.Body[i], n)
+				f.formatExpr(def.Body[i], stmtNode)
+				f.tailCalls = prevTailCalls
 			}
 			delete(f.seenUDFs, def)
 		} else {
@@ -998,6 +1007,10 @@ func (f *ExprFmtCtx) formatScalarWithLabel(
 		if !udf.Def.CalledOnNullInput {
 			tp.Child("strict")
 		}
+		if _, tailCall := f.tailCalls[udf]; tailCall {
+			// This routine is in tail-call position in the parent routine.
+			tp.Child("tail-call")
+		}
 		formatRoutineArgs(udf.Args, tp)
 		formatUDFDefinition(udf.Def, tp)
 	}