diff --git a/src/query/src/qAggMain.c b/src/query/src/qAggMain.c
index 9019a01eeff87414e917923666d2e4d842e3d12c..1db8f8233e487d47d4af8bab51767e22b6e42fe6 100644
--- a/src/query/src/qAggMain.c
+++ b/src/query/src/qAggMain.c
@@ -4032,11 +4032,23 @@ static void irate_function(SQLFunctionCtx *pCtx) {
     double v = 0;
     GET_TYPED_DATA(v, double, pCtx->inputType, pData);
 
-    if ((INT64_MIN == pRateInfo->lastKey) || primaryKey[i] > pRateInfo->lastKey) {
+    if (INT64_MIN == pRateInfo->lastKey) {
       pRateInfo->lastValue = v;
       pRateInfo->lastKey   = primaryKey[i];
       continue;
     }
+
+    if (primaryKey[i] > pRateInfo->lastKey) {
+      if ((INT64_MIN == pRateInfo->firstKey) || pRateInfo->lastKey > pRateInfo->firstKey) {
+        pRateInfo->firstValue = pRateInfo->lastValue;
+        pRateInfo->firstKey = pRateInfo->lastKey;
+      }
+
+      pRateInfo->lastValue = v;
+      pRateInfo->lastKey   = primaryKey[i];
+      
+      continue;
+    }
     
     if ((INT64_MIN == pRateInfo->firstKey) || primaryKey[i] > pRateInfo->firstKey) {
       pRateInfo->firstValue = v;
diff --git a/tests/script/general/parser/function.sim b/tests/script/general/parser/function.sim
index 556292b21b218f4df2aaa034d8babe35903a23b8..48e52cc7d7f946a18c366fc1ba667daf3fcf55eb 100644
--- a/tests/script/general/parser/function.sim
+++ b/tests/script/general/parser/function.sim
@@ -941,6 +941,17 @@ if $data32 != 0.000144445 then
   return -1
 endi
 
+sql insert into t1 values('2015-09-18 00:30:00', 3.0);
+sql select irate(k) from t1
+if $rows != 1 then
+  return -1
+endi
+
+if $data00 != 0.000000354 then
+  return -1
+endi
+
+
 print ===========================> derivative
 sql drop table t1
 sql drop table tx;