ovsdb-idlc: Make no-op writes to write-only columns cheaper.

[sliver-openvswitch.git] / lib / ovsdb-idl.c

diff --git a/lib/ovsdb-idl.c b/lib/ovsdb-idl.c
index fbf4bba..0c644a5 100644 (file)
--- a/lib/ovsdb-idl.c
+++ b/lib/ovsdb-idl.c
@@ -1826,10 +1826,10 @@ ovsdb_idl_txn_complete(struct ovsdb_idl_txn *txn,
  * Takes ownership of what 'datum' points to (and in some cases destroys that
  * data before returning) but makes a copy of 'datum' itself.  (Commonly
  * 'datum' is on the caller's stack.) */
-void
-ovsdb_idl_txn_write(const struct ovsdb_idl_row *row_,
-                    const struct ovsdb_idl_column *column,
-                    struct ovsdb_datum *datum)
+static void
+ovsdb_idl_txn_write__(const struct ovsdb_idl_row *row_,
+                      const struct ovsdb_idl_column *column,
+                      struct ovsdb_datum *datum, bool owns_datum)
 {
     struct ovsdb_idl_row *row = CONST_CAST(struct ovsdb_idl_row *, row_);
     const struct ovsdb_idl_table_class *class;
@@ -1837,8 +1837,7 @@ ovsdb_idl_txn_write(const struct ovsdb_idl_row *row_,
     bool write_only;
 
     if (ovsdb_idl_row_is_synthetic(row)) {
-        ovsdb_datum_destroy(datum, &column->type);
-        return;
+        goto discard_datum;
     }
 
     class = row->table->class;
@@ -1853,8 +1852,7 @@ ovsdb_idl_txn_write(const struct ovsdb_idl_row *row_,
     if (row->table->idl->verify_write_only && !write_only) {
         VLOG_ERR("Bug: Attempt to write to a read/write column (%s:%s) when"
                  " explicitly configured not to.", class->name, column->name);
-        ovsdb_datum_destroy(datum, &column->type);
-        return;
+        goto discard_datum;
     }
 
     /* If this is a write-only column and the datum being written is the same
@@ -1870,8 +1868,7 @@ ovsdb_idl_txn_write(const struct ovsdb_idl_row *row_,
      * ovsdb_idl_txn_commit().) */
     if (write_only && ovsdb_datum_equals(ovsdb_idl_read(row, column),
                                          datum, &column->type)) {
-        ovsdb_datum_destroy(datum, &column->type);
-        return;
+        goto discard_datum;
     }
 
     if (hmap_node_is_null(&row->txn_node)) {
@@ -1889,9 +1886,36 @@ ovsdb_idl_txn_write(const struct ovsdb_idl_row *row_,
     } else {
         bitmap_set1(row->written, column_idx);
     }
-    row->new[column_idx] = *datum;
+    if (owns_datum) {
+        row->new[column_idx] = *datum;
+    } else {
+        ovsdb_datum_clone(&row->new[column_idx], datum, &column->type);
+    }
     (column->unparse)(row);
     (column->parse)(row, &row->new[column_idx]);
+    return;
+
+discard_datum:
+    if (owns_datum) {
+        ovsdb_datum_destroy(datum, &column->type);
+    }
+}
+
+void
+ovsdb_idl_txn_write(const struct ovsdb_idl_row *row,
+                    const struct ovsdb_idl_column *column,
+                    struct ovsdb_datum *datum)
+{
+    ovsdb_idl_txn_write__(row, column, datum, true);
+}
+
+void
+ovsdb_idl_txn_write_clone(const struct ovsdb_idl_row *row,
+                          const struct ovsdb_idl_column *column,
+                          const struct ovsdb_datum *datum)
+{
+    ovsdb_idl_txn_write__(row, column,
+                          CONST_CAST(struct ovsdb_datum *, datum), false);
 }
 
 /* Causes the original contents of 'column' in 'row_' to be verified as a