Improve regex parsing of CHECK constraints for PostgreSQL.

Fixed issue where the PostgreSQL dialect would fail to parse a reflected
CHECK constraint that was a boolean-valued function (as opposed to a
boolean-valued expression).

Fixes: #5039
Closes: #5044
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/5044
Pull-request-sha: b6903c656422abf658c4cc88b8cd03291d3a50f8

Change-Id: I7d39b104a8ce346cb593d541c1b4e5eab88867f9

1 files changed, 3 insertions, 2 deletions

diff --git a/lib/sqlalchemy/dialects/postgresql/base.py b/lib/sqlalchemy/dialects/postgresql/base.py
index cbc750066..e8e79b230 100644
--- a/lib/sqlalchemy/dialects/postgresql/base.py
+++ b/lib/sqlalchemy/dialects/postgresql/base.py
@@ -3485,12 +3485,13 @@ class PGDialect(default.DefaultDialect):
             # "CHECK (((a > 1) AND (a < 5)))"
             # "CHECK (((a = 1) OR ((a > 2) AND (a < 5))))"
             # "CHECK (((a > 1) AND (a < 5))) NOT VALID"
-            m = re.match(r"^CHECK *\(\((.+)\)\)( NOT VALID)?$", src)
+            # "CHECK (some_boolean_function(a))"
+            m = re.match(r"^CHECK *\((.+)\)( NOT VALID)?$", src)
             if not m:
                 util.warn("Could not parse CHECK constraint text: %r" % src)
                 sqltext = ""
             else:
-                sqltext = m.group(1)
+                sqltext = re.sub(r'^\((.+)\)$', r'\1', m.group(1))
             entry = {"name": name, "sqltext": sqltext}
             if m and m.group(2):
                 entry["dialect_options"] = {"not_valid": True}