commit 65af5d3bc4d9d1476bfb6eb39a35397cd0b75873
Author: Matthew Radcliffe <mradcliffe@softpixel.com>
Date:   Sat Feb 7 15:53:15 2015 -0500

    Issue #1600670 by mradcliffe: Add unit test cases first, and refactor fix based on that. This no longer quotes every identifier, and only deals with case-sensitivity for now as that is what the base driver supports out of the box.

diff --git a/core/lib/Drupal/Core/Database/Driver/pgsql/Connection.php b/core/lib/Drupal/Core/Database/Driver/pgsql/Connection.php
index 0745e29..daa91f9 100644
--- a/core/lib/Drupal/Core/Database/Driver/pgsql/Connection.php
+++ b/core/lib/Drupal/Core/Database/Driver/pgsql/Connection.php
@@ -190,17 +190,31 @@ public function queryTemporary($query, array $args = array(), array $options = a
    * Escapes a field name string.
    *
    * Force all field names to be strictly alphanumeric-plus-underscore.
-   * The pgsql database drivers supports wrapping the field name in
-   * double quotes.
+   * The pgsql database driver supports case-sensitive field names, but do not
+   * support field names that contain periods despite being valid in
+   * PostgreSQL. This is because escapeField() may be called by a field with
+   * a table alias as part of SQL conditions or order by statements.
    *
    * @return string
    *   The sanitized field name string.
    */
   public function escapeField($field) {
-    $escaped = preg_replace('/^[^A-Za-z0-9_][^A-Za-z0-9_.]+/', '', $field);
+    $escaped = parent::escapeField($field);
 
-    // Check for beginning and ending double quote.
-    if (preg_match('/^["]/', $field) && preg_match('/["]$/', $field)) {
+    // Escape any invalid start character.
+    $escaped = preg_replace('/^[^A-Za-z0-9_]/', '', $escaped);
+
+    // Consider a period as a table alias identifier, and split the string.
+    if (preg_match('/^([A-Za-z0-9_]+)"?[.]"?([A-Za-z0-9_.]+)/', $escaped, $parts)) {
+      $table = $parts[1];
+      $column = $parts[2];
+
+      // Use escape alias because escapeField may contain multiple periods that
+      // need to be escaped.
+      $escaped = $this->escapeTable($table) . '.' . $this->escapeAlias($column);
+    }
+    elseif (preg_match('/[A-Z]/', $escaped)) {
+      // Quote the field name for case-sensitivity.
       $escaped = '"' . $escaped . '"';
     }
 
@@ -213,8 +227,12 @@ public function escapeField($field) {
   public function escapeAlias($field) {
     $escaped = preg_replace('/[^A-Za-z0-9_]+/', '', $field);
 
-    // Escape the alias in quotes
-    return '"' . $escaped . '"';
+    // Escape the alias in quotes for case-sensitivity.
+    if (preg_match('/[A-Z]/', $escaped)) {
+      $escaped = '"' . $escaped . '"';
+    }
+
+    return $escaped;
   }
 
   /**
@@ -223,8 +241,8 @@ public function escapeAlias($field) {
   public function escapeTable($table) {
     $escaped = parent::escapeTable($table);
 
-    // Check for beginning and ending double quote.
-    if (preg_match('/^["]/', $table) && preg_match('/["]$/', $table)) {
+    // Quote identifier to make it case-sensitive.
+    if (preg_match('/[A-Z]/', $escaped)) {
       $escaped = '"' . $escaped . '"';
     }
 
diff --git a/core/tests/Drupal/Tests/Core/Database/Driver/pgsql/PostgresqlConnectionTest.php b/core/tests/Drupal/Tests/Core/Database/Driver/pgsql/PostgresqlConnectionTest.php
index 7884b15..17de10c 100644
--- a/core/tests/Drupal/Tests/Core/Database/Driver/pgsql/PostgresqlConnectionTest.php
+++ b/core/tests/Drupal/Tests/Core/Database/Driver/pgsql/PostgresqlConnectionTest.php
@@ -39,7 +39,10 @@ protected function setUp() {
    */
   public function providerEscapeTables() {
     return array(
+      array('nocase', 'nocase'),
+      array('"camelCase"', 'camelCase'),
       array('"camelCase"', '"camelCase"'),
+      array('"camelCase"', 'camel/Case'),
     );
   }
 
@@ -54,7 +57,10 @@ public function providerEscapeTables() {
    */
   public function providerEscapeAliases() {
     return array(
-      array('"camelCase"', '"camelCase"')
+      array('nocase', 'nocase'),
+      array('"camelCase"', '"camelCase"'),
+      array('"camelCase"', 'camelCase'),
+      array('"camelCase"', 'camel.Case'),
     );
   }
 
@@ -68,7 +74,14 @@ public function providerEscapeAliases() {
    */
   public function providerEscapeFields() {
     return array(
-      array('""isDefaultRevision""', '"isDefaultRevision"')
+      array('title', 'title'),
+      array('"isDefaultRevision"', 'isDefaultRevision'),
+      array('"isDefaultRevision"', '"isDefaultRevision"'),
+      array('entity_test."isDefaultRevision"', 'entity_test.isDefaultRevision'),
+      array('entity_test."isDefaultRevision"', '"entity_test"."isDefaultRevision"'),
+      array('"entityTest"."isDefaultRevision"', '"entityTest"."isDefaultRevision"'),
+      array('"entityTest"."isDefaultRevision"', 'entityTest.isDefaultRevision'),
+      array('entity_test."isDefaultRevision"', 'entity_test.is.Default.Revision'),
     );
   }