diff options
Diffstat (limited to 'src/include/nodes/primnodes.h')
| -rw-r--r-- | src/include/nodes/primnodes.h | 28 |
1 files changed, 18 insertions, 10 deletions
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h index 4eea81446b2..10e51e40268 100644 --- a/src/include/nodes/primnodes.h +++ b/src/include/nodes/primnodes.h @@ -6,7 +6,7 @@ * * Copyright (c) 1994, Regents of the University of California * - * $Id: primnodes.h,v 1.34 1999/08/21 03:49:09 tgl Exp $ + * $Id: primnodes.h,v 1.35 1999/08/22 20:15:00 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -120,15 +120,23 @@ typedef struct Expr /* ---------------- * Var * varno - index of this var's relation in the range table - * (could be INNER or OUTER) + * (could also be INNER or OUTER) * varattno - attribute number of this var, or zero for all - * vartype - pg_type tuple oid for the type of this var + * vartype - pg_type tuple OID for the type of this var * vartypmod - pg_attribute typmod value - * varlevelsup - for subquery variables referencing outer relations - * varnoold - keep varno around in case it got changed to INNER/ - * OUTER (see match_varid) - * varoattno - attribute number of this var - * [ '(varnoold varoattno) was varid -ay 2/95] + * varlevelsup - for subquery variables referencing outer relations; + * 0 in a normal var, >0 means N levels up + * varnoold - original value of varno + * varoattno - original value of varattno + * + * Note: during parsing/planning, varnoold/varoattno are always just copies + * of varno/varattno. At the tail end of planning, Var nodes appearing in + * upper-level plan nodes are reassigned to point to the outputs of their + * subplans; for example, in a join node varno becomes INNER or OUTER and + * varattno becomes the index of the proper element of that subplan's target + * list. But varnoold/varoattno continue to hold the original values. + * The code doesn't really need varnoold/varoattno, but they are very useful + * for debugging and interpreting completed plans, so we keep them around. * ---------------- */ #define INNER 65000 @@ -145,8 +153,8 @@ typedef struct Var Oid vartype; int32 vartypmod; Index varlevelsup; /* erased by upper optimizer */ - Index varnoold; /* only used by optimizer */ - AttrNumber varoattno; /* only used by optimizer */ + Index varnoold; /* mainly for debugging --- see above */ + AttrNumber varoattno; } Var; /* ---------------- |