From ba55bed00820e12f0d55898ee1a9917644cb4b73 Mon Sep 17 00:00:00 2001
From: Miroslav Stampar <miroslav.stampar@gmail.com>
Date: Thu, 25 Oct 2012 10:41:16 +0200
Subject: [PATCH] More general approach for PostgreSQL concatenation operator
 precedence problem (Issue #219)

---
 plugins/dbms/postgresql/syntax.py | 9 +++++++--
 plugins/generic/databases.py      | 2 +-
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/plugins/dbms/postgresql/syntax.py b/plugins/dbms/postgresql/syntax.py
index 47cf95b52..de0580ae9 100644
--- a/plugins/dbms/postgresql/syntax.py
+++ b/plugins/dbms/postgresql/syntax.py
@@ -14,6 +14,11 @@ class Syntax(GenericSyntax):
 
     @staticmethod
     def unescape(expression, quote=True):
+        """
+        Note: PostgreSQL has a general problem with concenation operator (||) precedence (hence the parentheses enclosing)
+              e.g. SELECT 1 WHERE 'a'!='a'||'b' will trigger error ("argument of WHERE must be type boolean, not type text")
+        """
+
         if quote:
             while True:
                 index = expression.find("'")
@@ -28,11 +33,11 @@ class Syntax(GenericSyntax):
 
                 lastIndex = firstIndex + index
                 old = "'%s'" % expression[firstIndex:lastIndex]
-                unescaped = "||".join("CHR(%d)" % (ord(expression[i])) for i in xrange(firstIndex, lastIndex))  # Postgres CHR() function already accepts Unicode code point of character(s)
+                unescaped = "(%s)" % "||".join("CHR(%d)" % (ord(expression[i])) for i in xrange(firstIndex, lastIndex))  # Postgres CHR() function already accepts Unicode code point of character(s)
 
                 expression = expression.replace(old, unescaped)
         else:
-            expression = "||".join("CHR(%d)" % ord(c) for c in expression)
+            expression = "(%s)" % "||".join("CHR(%d)" % ord(c) for c in expression)
 
         return expression
 
diff --git a/plugins/generic/databases.py b/plugins/generic/databases.py
index 890c19cb6..f874f2f51 100644
--- a/plugins/generic/databases.py
+++ b/plugins/generic/databases.py
@@ -256,7 +256,7 @@ class Databases:
             if condition:
                 if conf.excludeSysDbs:
                     query += " WHERE "
-                    query += " AND ".join("%s != ('%s')" % (condition, unsafeSQLIdentificatorNaming(db)) for db in self.excludeDbsList)
+                    query += " AND ".join("%s != '%s'" % (condition, unsafeSQLIdentificatorNaming(db)) for db in self.excludeDbsList)
                     infoMsg = "skipping system database%s '%s'" % ("s" if len(self.excludeDbsList) > 1 else "", ", ".join(db for db in self.excludeDbsList))
                     logger.info(infoMsg)
                 elif not Backend.isDbms(DBMS.SQLITE):