Merge #111329

111329: plpgsql: add support for unnamed cursors r=DrewKimball a=DrewKimball

#### plpgsql: add builtin to generate unique cursor names

This patch adds a builtin function `crdb_internal.plpgsql_gen_cursor_name`
that generates a unique name for a PLpgSQL cursor if the supplied name
is NULL. It then returns the resulting name to be used when opening
a cursor. This will be used in a following commit to implement unnamed
PLpgSQL cursors.

Informs #109709

Release note: None

#### plpgsql: add support for unnamed cursors

This patch adds support for opening an "unnamed" cursor in a PLpgSQL
routine. A PLpgSQL cursor is unnamed when the value for the cursor
variable is `NULL`. When an unnamed cursor is opened, a name will be
generated for it like `<unnamed portal 1>` that is guaranteed not to
conflict with an existing cursor or portal name. The PLpgSQL variable
that represents the cursor's name is updated to reflect the generated
name.

Informs #109709

Release note (sql change): Added support for unnamed PLpgSQL cursors,
which generate a unique name when no cursor name was specified.

Co-authored-by: Drew Kimball <[email protected]>

pkg/sql/faketreeeval/evalctx.go

@@ -333,6 +333,11 @@ func (*DummyEvalPlanner) Optimizer() interface{} {
 	return nil
 }
 
+// GenUniqueCursorName is part of the eval.Planner interface.
+func (*DummyEvalPlanner) GenUniqueCursorName() tree.Name {
+	return ""
+}
+
 var _ eval.Planner = &DummyEvalPlanner{}
 
 var errEvalPlanner = pgerror.New(pgcode.ScalarOperationCannotRunWithoutFullSessionContext,

pkg/sql/logictest/testdata/logic_test/plpgsql_builtins

@@ -0,0 +1,95 @@
+# Testing crdb_internal.plpgsql_gen_cursor_name.
+query T
+SELECT crdb_internal.plpgsql_gen_cursor_name(NULL);
+----
+<unnamed portal 1>
+
+query T
+SELECT crdb_internal.plpgsql_gen_cursor_name(NULL);
+----
+<unnamed portal 2>
+
+statement ok
+BEGIN;
+DECLARE "<unnamed portal 3>" CURSOR FOR SELECT 1;
+
+query T
+SELECT name FROM pg_cursors;
+----
+<unnamed portal 3>
+
+# Skip manually generated duplicate names.
+query T
+SELECT crdb_internal.plpgsql_gen_cursor_name(NULL);
+----
+<unnamed portal 4>
+
+query T
+SELECT crdb_internal.plpgsql_gen_cursor_name(NULL);
+----
+<unnamed portal 5>
+
+statement ok
+CLOSE "<unnamed portal 3>";
+
+# Keep incrementing after a "gap" opens.
+query T
+SELECT crdb_internal.plpgsql_gen_cursor_name(NULL);
+----
+<unnamed portal 6>
+
+statement ok;
+ABORT;
+
+# Continue incrementing over transaction boundaries.
+query T
+SELECT crdb_internal.plpgsql_gen_cursor_name(NULL);
+----
+<unnamed portal 7>
+
+# If the name is already set, don't generate a new one.
+query T
+SELECT crdb_internal.plpgsql_gen_cursor_name('foo');
+----
+foo
+
+query T
+SELECT crdb_internal.plpgsql_gen_cursor_name('bar');
+----
+bar
+
+query T
+SELECT crdb_internal.plpgsql_gen_cursor_name('');
+----
+·
+
+query T
+SELECT crdb_internal.plpgsql_gen_cursor_name(NULL);
+----
+<unnamed portal 8>
+
+# Starting a new session restarts the counter.
+user testuser
+
+query T
+SELECT crdb_internal.plpgsql_gen_cursor_name(NULL);
+----
+<unnamed portal 1>
+
+query T
+SELECT crdb_internal.plpgsql_gen_cursor_name(NULL);
+----
+<unnamed portal 2>
+
+# Returning to the old session continues the old counter.
+user root
+
+query T
+SELECT crdb_internal.plpgsql_gen_cursor_name(NULL);
+----
+<unnamed portal 9>
+
+query T
+SELECT crdb_internal.plpgsql_gen_cursor_name(NULL);
+----
+<unnamed portal 10>