From: RYAN D. MOATS <rmo...@us.ibm.com>
Change tracking is a bit different from what someone with
"classic" database experience might expect, so let's add
the knowledged gained from the experience of making change
tracking work for incremental processing.
Signed-off-by: RYAN D. MOATS <rmo...@us.ibm.com>
---
lib/ovsdb-idl.h | 10 +++++++++-
1 files changed, 9 insertions(+), 1 deletions(-)
diff --git a/lib/ovsdb-idl.h b/lib/ovsdb-idl.h
index bad2dc6..538602c 100644
--- a/lib/ovsdb-idl.h
+++ b/lib/ovsdb-idl.h
@@ -113,7 +113,15 @@ void ovsdb_idl_add_table(struct ovsdb_idl *,
void ovsdb_idl_omit(struct ovsdb_idl *, const struct ovsdb_idl_column *);
void ovsdb_idl_omit_alert(struct ovsdb_idl *, const struct ovsdb_idl_column *);
-/* Change tracking. */
+/* Change tracking. In OVSDB, change tracking is applied at each client in
+ * the IDL layer. This means that when a client makes a request to track
+ * changes on a particular table, they are essentially requesting
+ * information about the incremental changes to that table from the point in
+ * time that the request is made. Once the client clears tracked changes,
+ * that information will no longer be available. The implication of this
+ * is that it is not a simple matter for code to "replay" changes from the
+ * past. Rather, code should be structured with a path for processing the
+ * full table as well as a path that processes incremental changes. */
enum ovsdb_idl_change {
OVSDB_IDL_CHANGE_INSERT,
OVSDB_IDL_CHANGE_MODIFY,
--
1.7.1
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