sql: add CACHE clause to SHOW CREATE SEQUENCE when relevant

In 21.1 we added support for `CACHE` to sequences but we didn't add the logic
to render that clause.

Release note (bug fix): Render `CACHE` clause for sequences which use a cache.

pkg/sql/logictest/testdata/logic_test/sequences

@@ -1485,6 +1485,11 @@ CREATE SEQUENCE cache_test CACHE 0
 statement ok
 CREATE SEQUENCE cache_test CACHE 10 INCREMENT 1
 
+query TT
+SHOW CREATE SEQUENCE cache_test
+----
+cache_test  CREATE SEQUENCE public.cache_test MINVALUE 1 MAXVALUE 9223372036854775807 INCREMENT 1 START 1 CACHE 10
+
 # Verify cache invalidation with schema changes.
 
 # 10 values (1,2,...,10) are cached, and the underlying sequence is incremented to 10.

pkg/sql/show_create_clauses.go

@@ -248,6 +248,9 @@ func ShowCreateSequence(
 	if opts.Virtual {
 		f.Printf(" VIRTUAL")
 	}
+	if opts.CacheSize > 1 {
+		f.Printf(" CACHE %d", opts.CacheSize)
+	}
 	return f.CloseAndGetString(), nil
 }
 

pkg/sql/show_test.go

@@ -432,6 +432,14 @@ func TestShowCreateSequence(t *testing.T) {
 			`CREATE SEQUENCE %s INCREMENT 5 MAXVALUE 10000 START 10 MINVALUE 0`,
 			`CREATE SEQUENCE public.%s MINVALUE 0 MAXVALUE 10000 INCREMENT 5 START 10`,
 		},
+		{
+			`CREATE SEQUENCE %s INCREMENT 5 MAXVALUE 10000 START 10 MINVALUE 0 CACHE 1`,
+			`CREATE SEQUENCE public.%s MINVALUE 0 MAXVALUE 10000 INCREMENT 5 START 10`,
+		},
+		{
+			`CREATE SEQUENCE %s INCREMENT 5 MAXVALUE 10000 START 10 MINVALUE 0 CACHE 10`,
+			`CREATE SEQUENCE public.%s MINVALUE 0 MAXVALUE 10000 INCREMENT 5 START 10 CACHE 10`,
+		},
 	}
 	for i, test := range tests {
 		t.Run(fmt.Sprint(i), func(t *testing.T) {