[FIX] Workaround to fix error when creating a corpus with a long query

gargantext/models/base.py

 from sqlalchemy.schema import Column, ForeignKey, UniqueConstraint, Index
-from sqlalchemy.orm import relationship
+from sqlalchemy.orm import relationship, validates
 from sqlalchemy.types import TypeDecorator, \
                              Integer, Float, Boolean, DateTime, String, Text
 from sqlalchemy.dialects.postgresql import JSONB, DOUBLE_PRECISION as Double
@@ -7,6 +7,7 @@ from sqlalchemy.ext.mutable import MutableDict, MutableList
 from sqlalchemy.ext.declarative import declarative_base
 
 __all__ = ["Column", "ForeignKey", "UniqueConstraint", "relationship",
+           "validates", "ValidatorMixin",
            "Integer", "Float", "Boolean", "DateTime", "String", "Text",
            "TypeDecorator",
            "JSONB", "Double",
@@ -18,6 +19,25 @@ __all__ = ["Column", "ForeignKey", "UniqueConstraint", "relationship",
 # all tables handled by Alembic migration scripts.
 Base = declarative_base()
 
+
 # To be used by tables already handled by Django ORM, such as User model. We
 # separate them in order to keep those out of Alembic sight.
 DjangoBase = declarative_base()
+
+
+class ValidatorMixin(object):
+    def enforce_length(self, key, value):
+        """Truncate a string according to its column length
+
+        Usage example:
+
+        .. code-block:: python
+
+            @validates('some_column')
+            def validate_some_column(self, key, value):
+                self.enforce_length(key, value)
+        """
+        max_len = getattr(self.__class__, key).prop.columns[0].type.length
+        if value and len(value) > max_len:
+            return value[:max_len]
+        return value

gargantext/models/nodes.py

@@ -9,7 +9,7 @@ from datetime import datetime
 
 from .base import Base, Column, ForeignKey, relationship, TypeDecorator, Index, \
                   Integer, Float, String, DateTime, JSONB, \
-                  MutableList, MutableDict
+                  MutableList, MutableDict, validates, ValidatorMixin
 from .users import User
 
 __all__ = ['Node', 'NodeNode', 'CorpusNode']
@@ -26,7 +26,7 @@ class NodeType(TypeDecorator):
         return NODETYPES[typeindex]
 
 
-class Node(Base):
+class Node(ValidatorMixin, Base):
     """This model can fit many purposes:
 
     myFirstCorpus = session.query(CorpusNode).first()
@@ -112,6 +112,10 @@ class Node(Base):
                'user_id={0.user_id}, parent_id={0.parent_id}, ' \
                'name={0.name!r}, date={0.date})>'.format(self)
 
+    @validates('name')
+    def validate_name(self, key, value):
+        return self.enforce_length(key, value)
+
     @property
     def ngrams(self):
         """Pseudo-attribute allowing to retrieve a node's ngrams.