From 06bc23f38801371c60e97b8f71ee7ce7719160fd Mon Sep 17 00:00:00 2001
From: Dirk Zimoch <dirk.zimoch@psi.ch>
Date: Fri, 30 Aug 2024 11:58:12 +0200
Subject: [PATCH] send DBE_PROPERTY events only if property field actually
 changed

---
 modules/database/src/ioc/db/dbAccess.c | 27 +++++++++++++++++++-------
 1 file changed, 20 insertions(+), 7 deletions(-)

diff --git a/modules/database/src/ioc/db/dbAccess.c b/modules/database/src/ioc/db/dbAccess.c
index 21f5f0b64a..2a943f9314 100644
--- a/modules/database/src/ioc/db/dbAccess.c
+++ b/modules/database/src/ioc/db/dbAccess.c
@@ -1325,6 +1325,7 @@ long dbPut(DBADDR *paddr, short dbrType,
     long status = 0;
     dbFldDes *pfldDes;
     int isValueField;
+    int propertyUpdate = 0;
 
     if (special == SPC_ATTRIBUTE)
         return S_db_noMod;
@@ -1369,8 +1370,23 @@ long dbPut(DBADDR *paddr, short dbrType,
         if (nRequest < 1) {
             recGblSetSevr(precord, LINK_ALARM, INVALID_ALARM);
         } else {
-            status = dbFastPutConvertRoutine[dbrType][field_type](pbuffer,
-                paddr->pfield, paddr);
+            propertyUpdate = paddr->pfldDes->prop && precord->mlis.count;
+            if (propertyUpdate && paddr->field_size <= sizeof(epicsAny)) {
+                epicsAny propBuffer;
+                status = dbFastPutConvertRoutine[dbrType][field_type](pbuffer,
+                    &propBuffer, paddr);
+                if (!status) {
+                    if (memcmp(paddr->pfield, &propBuffer, paddr->field_size) != 0) {
+                        memcpy(paddr->pfield, &propBuffer, paddr->field_size);
+                    } else {
+                        /* suppress DBE_PROPERTY event if property did not change */
+                        propertyUpdate = 0;
+                    }
+                }
+            } else {
+                status = dbFastPutConvertRoutine[dbrType][field_type](pbuffer,
+                    paddr->pfield, paddr);
+            }
             nRequest = 1;
         }
     }
@@ -1391,12 +1407,9 @@ long dbPut(DBADDR *paddr, short dbrType,
     if (precord->mlis.count &&
         !(isValueField && pfldDes->process_passive))
         db_post_events(precord, pfieldsave, DBE_VALUE | DBE_LOG);
-    /* If this field is a property (metadata) field,
-     * then post a property change event (even if the field
-     * didn't change).
-     */
-    if (precord->mlis.count && pfldDes->prop)
+    if (propertyUpdate) {
         db_post_events(precord, NULL, DBE_PROPERTY);
+    }
 done:
     paddr->pfield = pfieldsave;
     return status;