diff options
Diffstat (limited to 'src/include/nodes/relation.h')
| -rw-r--r-- | src/include/nodes/relation.h | 16 |
1 files changed, 3 insertions, 13 deletions
diff --git a/src/include/nodes/relation.h b/src/include/nodes/relation.h index c0a636b9d7c..b611e0b905a 100644 --- a/src/include/nodes/relation.h +++ b/src/include/nodes/relation.h @@ -1465,18 +1465,9 @@ typedef struct AppendRelInfo * then allow it to bubble up like a Var until the ph_needed join level. * ph_needed has the same definition as attr_needed for a regular Var. * - * ph_may_need is an initial estimate of ph_needed, formed using the - * syntactic locations of references to the PHV. We need this in order to - * determine whether the PHV reference forces a join ordering constraint: - * if the PHV has to be evaluated below the nullable side of an outer join, - * and then used above that outer join, we must constrain join order to ensure - * there's a valid place to evaluate the PHV below the join. The final - * actual ph_needed level might be lower than ph_may_need, but we can't - * determine that until later on. Fortunately this doesn't matter for what - * we need ph_may_need for: if there's a PHV reference syntactically - * above the outer join, it's not going to be allowed to drop below the outer - * join, so we would come to the same conclusions about join order even if - * we had the final ph_needed value to compare to. + * Notice that when ph_eval_at is a join rather than a single baserel, the + * PlaceHolderInfo may create constraints on join order: the ph_eval_at join + * has to be formed below any outer joins that should null the PlaceHolderVar. * * We create a PlaceHolderInfo only after determining that the PlaceHolderVar * is actually referenced in the plan tree, so that unreferenced placeholders @@ -1491,7 +1482,6 @@ typedef struct PlaceHolderInfo PlaceHolderVar *ph_var; /* copy of PlaceHolderVar tree */ Relids ph_eval_at; /* lowest level we can evaluate value at */ Relids ph_needed; /* highest level the value is needed at */ - Relids ph_may_need; /* highest level it might be needed at */ int32 ph_width; /* estimated attribute width */ } PlaceHolderInfo; |