[Sqlalchemy-tickets] Issue #3999: merge operator precedence for all like / is / eq / comparison to 5 (zzzeek/sqlalchemy)

[Michael B. <iss...@bi...>]

New issue 3999: merge operator precedence for all like / is / eq / comparison to 5
https://bitbucket.org/zzzeek/sqlalchemy/issues/3999/merge-operator-precedence-for-all-like-is

Michael Bayer:

e.g.:

```
#!diff


diff --git a/lib/sqlalchemy/sql/operators.py b/lib/sqlalchemy/sql/operators.py
index 58f32b3..ca5a90b 100644
--- a/lib/sqlalchemy/sql/operators.py
+++ b/lib/sqlalchemy/sql/operators.py
@@ -1094,15 +1094,15 @@ _PRECEDENCE = {
     match_op: 6,
     notmatch_op: 6,
 
-    ilike_op: 6,
-    notilike_op: 6,
-    like_op: 6,
-    notlike_op: 6,
-    in_op: 6,
-    notin_op: 6,
-
-    is_: 6,
-    isnot: 6,
+    ilike_op: 5,
+    notilike_op: 5,
+    like_op: 5,
+    notlike_op: 5,
+    in_op: 5,
+    notin_op: 5,
+
+    is_: 5,
+    isnot: 5,
 
     eq: 5,
     ne: 5,

```

rationale:  MySQL, Oracle and now Postgresql all have relatively flat precedences for these operators:

(mysql):
https://docs.oracle.com/cd/E17952_01/mysql-5.5-en/operator-precedence.html

(oracle):

https://docs.oracle.com/cd/B19306_01/server.102/b14200/conditions001.htm#i1034834

pg 9.4, less flat: https://www.postgresql.org/docs/9.4/static/sql-syntax-lexical.html#SQL-PRECEDENCE-TABLE

pg 9.5, now is more flat: https://www.postgresql.org/docs/9.5/static/sql-syntax-lexical.html#SQL-PRECEDENCE-TABLE

making these all have the same precedence means we'll just have more parenthesis.