Support Postgresql INTERVAL fields spec/reflection

Added support for all possible "fields" identifiers when reflecting the
Postgresql ``INTERVAL`` datatype, e.g. "YEAR", "MONTH", "DAY TO
MINUTE", etc..   In addition, the :class:`.postgresql.INTERVAL`
datatype itself now includes a new parameter
:paramref:`.postgresql.INTERVAL.fields` where these qualifiers can be
specified; the qualifier is also reflected back into the resulting
datatype upon reflection / inspection.

Change-Id: I33816e68c533b023e0632db6f4e73fefd2de4721
Fixes: #3959

1 files changed, 22 insertions, 8 deletions

diff --git a/lib/sqlalchemy/dialects/postgresql/base.py b/lib/sqlalchemy/dialects/postgresql/base.py
index 92009450e..802c6a905 100644
--- a/lib/sqlalchemy/dialects/postgresql/base.py
+++ b/lib/sqlalchemy/dialects/postgresql/base.py
@@ -962,8 +962,19 @@ class INTERVAL(sqltypes.TypeEngine):
     """
     __visit_name__ = 'INTERVAL'
 
-    def __init__(self, precision=None):
+    def __init__(self, precision=None, fields=None):
+        """Construct an INTERVAL.
+
+        :param precision: optional integer precision value
+        :param fields: string fields specifier.  allows storage of fields
+         to be limited, such as ``"YEAR"``, ``"MONTH"``, ``"DAY TO HOUR"``,
+         etc.
+
+         .. versionadded:: 1.2
+
+        """
         self.precision = precision
+        self.fields = fields
 
     @classmethod
     def _adapt_from_generic_interval(cls, interval):
@@ -1301,8 +1312,6 @@ ischema_names = {
     'bytea': BYTEA,
     'boolean': BOOLEAN,
     'interval': INTERVAL,
-    'interval year to month': INTERVAL,
-    'interval day to second': INTERVAL,
     'tsvector': TSVECTOR
 }
 
@@ -1827,10 +1836,12 @@ class PGTypeCompiler(compiler.GenericTypeCompiler):
         )
 
     def visit_INTERVAL(self, type_, **kw):
+        text = "INTERVAL"
+        if type_.fields is not None:
+            text += " " + type_.fields
         if type_.precision is not None:
-            return "INTERVAL(%d)" % type_.precision
-        else:
-            return "INTERVAL"
+            text += " (%d)" % type_.precision
+        return text
 
     def visit_BIT(self, type_, **kw):
         if type_.varying:
@@ -2489,10 +2500,13 @@ class PGDialect(default.DefaultDialect):
                 args = (int(charlen),)
             else:
                 args = ()
-        elif attype in ('interval', 'interval year to month',
-                        'interval day to second'):
+        elif attype.startswith('interval'):
+            field_match = re.match(r'interval (.+)', attype, re.I)
             if charlen:
                 kwargs['precision'] = int(charlen)
+            if field_match:
+                kwargs['fields'] = field_match.group(1)
+            attype = "interval"
             args = ()
         elif charlen:
             args = (int(charlen),)