Introduce InvalidCommandId.

This allows a 32-bit field to represent an *optional* command ID
without a separate flag bit.

Andres Freund

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 31e868d4bc7a0ad23d7ade8230cabe116d6ee437..0591f3fd56210d3f4902fce03392f5fc12ec931b 100644 (file)
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -766,12 +766,12 @@ CommandCounterIncrement(void)
    if (currentCommandIdUsed)
    {
        currentCommandId += 1;
-       if (currentCommandId == FirstCommandId) /* check for overflow */
+       if (currentCommandId == InvalidCommandId)
        {
            currentCommandId -= 1;
            ereport(ERROR,
                    (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
-                    errmsg("cannot have more than 2^32-1 commands in a transaction")));
+                    errmsg("cannot have more than 2^32-2 commands in a transaction")));
        }
        currentCommandIdUsed = false;
 

diff --git a/src/include/c.h b/src/include/c.h
index 596118342dfc4e4ba32741a9a9f3296747047ce8..14bfdcd4dab5afd18dde7303517388b1a1ee5a24 100644 (file)
--- a/src/include/c.h
+++ b/src/include/c.h
@@ -368,6 +368,7 @@ typedef uint32 MultiXactOffset;
 typedef uint32 CommandId;
 
 #define FirstCommandId ((CommandId) 0)
+#define InvalidCommandId   (~(CommandId)0)
 
 /*
  * Array indexing support