Ensure escaping of percent signs in columns, parameters

Improved support for column names that contain percent signs in the string,
including repaired issues involving anoymous labels that also embedded a
column name with a percent sign in it, as well as re-established support
for bound parameter names with percent signs embedded on the psycopg2
dialect, using a late-escaping process similar to that used by the
cx_Oracle dialect.

* Added new constructor for _anonymous_label() that ensures incoming
  string tokens based on column or table names will have percent
  signs escaped; abstracts away the format of the label.

* generalized cx_Oracle's quoted_bind_names facility into the compiler
  itself, and leveraged this for the psycopg2 dialect's issue with
  percent signs in names as well.  the parameter substitution is now
  integrated with compiler.construct_parameters() as well as the
  recently reworked set_input_sizes(), reducing verbosity in the
  cx_Oracle dialect.

Fixes: #5653

Change-Id: Ia2ad13ea68b4b0558d410026e5a33f5cb3fbab2c

1 files changed, 8 insertions, 1 deletions

diff --git a/lib/sqlalchemy/dialects/postgresql/psycopg2.py b/lib/sqlalchemy/dialects/postgresql/psycopg2.py
index 2446604ba..72c36b4a8 100644
--- a/lib/sqlalchemy/dialects/postgresql/psycopg2.py
+++ b/lib/sqlalchemy/dialects/postgresql/psycopg2.py
@@ -644,7 +644,14 @@ class PGExecutionContext_psycopg2(PGExecutionContext):
 
 
 class PGCompiler_psycopg2(PGCompiler):
-    pass
+    def bindparam_string(self, name, **kw):
+        if "%" in name and not kw.get("post_compile", False):
+            # psycopg2 will not allow a percent sign in a
+            # pyformat parameter name even if it is doubled
+            kw["escaped_from"] = name
+            name = name.replace("%", "P")
+
+        return PGCompiler.bindparam_string(self, name, **kw)
 
 
 class PGIdentifierPreparer_psycopg2(PGIdentifierPreparer):