export patch

diff --git a/CRM/Export/Form/Select.php b/CRM/Export/Form/Select.php
index 182e4fdba8..2fa668f950 100644
--- a/CRM/Export/Form/Select.php
+++ b/CRM/Export/Form/Select.php
@@ -231,11 +231,23 @@ FROM   {$this->_componentTable}
       $this->assign('totalSelectedRecords', $rowCount);
     }
 
+    // If you have a large export and transfer data via $this->get() or $this->set(),
+    // it can overwhelm session storage limits. Use a temporary space.
+    $zCachePrefix = $this->get('zCachePrefix');
+    if (!$zCachePrefix) {
+      $zCachePrefix = 'CRM_Export_' . CRM_Utils_String::createRandom(16, CRM_Utils_String::ALPHANUMERIC);
+      $this->set('zCachePrefix', $zCachePrefix);
+    }
+    $zCacheTtl = 60 * 60;
+    $zCachePut = function($key, $data) use ($zCachePrefix, $zCacheTtl) {
+      Civi::cache('long')->set("{$zCachePrefix}_{$key}", gzencode(json_encode($data), 9), $zCacheTtl);
+    };
+
     $this->assign('matchingContacts', $this->_matchingContacts);
-    $this->set('componentIds', $this->_componentIds);
+    $zCachePut('componentIds', $this->_componentIds); // O(N)
     $this->set('selectAll', $this->_selectAll);
     $this->set('exportMode', $this->_exportMode);
-    $this->set('componentClause', $this->_componentClause);
+    $zCachePut('componentClause', $this->_componentClause); // O(N)
     $this->set('componentTable', $this->_componentTable);
   }
diff --git a/CRM/Export/Form/Map.php b/CRM/Export/Form/Map.php
index 38b961ae6b..122fe1bd3c 100644
--- a/CRM/Export/Form/Map.php
+++ b/CRM/Export/Form/Map.php
@@ -215,15 +215,25 @@ class CRM_Export_Form_Map extends CRM_Core_Form {
       }
     }
 
+    // Look up info retained from previous step
+    $zCachePrefix = $this->get('zCachePrefix');
+    $zCacheGet = function($key) use ($zCachePrefix) {
+      $raw = Civi::cache('long')->get("{$zCachePrefix}_{$key}");
+      if ($raw === NULL ) {
+        throw new \CRM_Core_Exception("Export process has expired or did not begin properly. Please start over.");
+      }
+      return json_decode(gzdecode($raw));
+    };
+
     //get the csv file
     CRM_Export_BAO_Export::exportComponents($this->get('selectAll'),
-      $this->get('componentIds'),
+      $zCacheGet('componentIds'),
       (array) $this->get('queryParams'),
       $this->get(CRM_Utils_Sort::SORT_ORDER),
       $mappedFields,
       $this->get('returnProperties'),
       $this->get('exportMode'),
-      $this->get('componentClause'),
+      $zCacheGet('componentClause'),
       $this->get('componentTable'),
       $this->get('mergeSameAddress'),
       $this->get('mergeSameHousehold'),