diff options
Diffstat (limited to 'src/include/nodes/primnodes.h')
| -rw-r--r-- | src/include/nodes/primnodes.h | 10 |
1 files changed, 8 insertions, 2 deletions
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h index 089f7362a6b..11e74a8d92b 100644 --- a/src/include/nodes/primnodes.h +++ b/src/include/nodes/primnodes.h @@ -10,7 +10,7 @@ * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * - * $Id: primnodes.h,v 1.70 2002/11/26 03:01:59 tgl Exp $ + * $Id: primnodes.h,v 1.71 2002/11/30 21:25:06 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -165,6 +165,12 @@ typedef enum CoercionForm /* * Expr + * + * Note: DISTINCT_EXPR implements the "x IS DISTINCT FROM y" construct. + * This is similar to an OP_EXPR, except for its handling of NULL inputs. + * The oper field is always an Oper node for the "=" operator for x and y. + * (We use "=", not the more obvious "<>", because more datatypes have "=" + * than "<>". This means the executor must invert the operator result.) */ typedef enum OpType { @@ -183,7 +189,7 @@ typedef struct Expr } Expr; /* - * Oper - Expr subnode for an OP_EXPR + * Oper - Expr subnode for an OP_EXPR (or DISTINCT_EXPR) * * NOTE: in the good old days 'opno' used to be both (or either, or * neither) the pg_operator oid, and/or the pg_proc oid depending |