diff options
Diffstat (limited to 'src/backend/optimizer/util/pathnode.c')
| -rw-r--r-- | src/backend/optimizer/util/pathnode.c | 21 |
1 files changed, 11 insertions, 10 deletions
diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c index 1158f7715bc..b60c88d9251 100644 --- a/src/backend/optimizer/util/pathnode.c +++ b/src/backend/optimizer/util/pathnode.c @@ -254,8 +254,9 @@ add_path(RelOptInfo *parent_rel, Path *new_path) { bool accept_new = true; /* unless we find a superior old path */ ListCell *insert_after = NULL; /* where to insert new item */ - ListCell *p1_prev = NULL; ListCell *p1; + ListCell *p1_prev; + ListCell *p1_next; /* * This is a convenient place to check for query cancel --- no part of the @@ -267,14 +268,19 @@ add_path(RelOptInfo *parent_rel, Path *new_path) * Loop to check proposed new path against old paths. Note it is possible * for more than one old path to be tossed out because new_path dominates * it. + * + * We can't use foreach here because the loop body may delete the current + * list cell. */ - p1 = list_head(parent_rel->pathlist); /* cannot use foreach here */ - while (p1 != NULL) + p1_prev = NULL; + for (p1 = list_head(parent_rel->pathlist); p1 != NULL; p1 = p1_next) { Path *old_path = (Path *) lfirst(p1); bool remove_old = false; /* unless new proves superior */ int costcmp; + p1_next = lnext(p1); + /* * As of Postgres 8.0, we use fuzzy cost comparison to avoid wasting * cycles keeping paths that are really not significantly different in @@ -343,20 +349,15 @@ add_path(RelOptInfo *parent_rel, Path *new_path) */ if (!IsA(old_path, IndexPath)) pfree(old_path); - /* Advance list pointer */ - if (p1_prev) - p1 = lnext(p1_prev); - else - p1 = list_head(parent_rel->pathlist); + /* p1_prev does not advance */ } else { /* new belongs after this old path if it has cost >= old's */ if (costcmp >= 0) insert_after = p1; - /* Advance list pointers */ + /* p1_prev advances */ p1_prev = p1; - p1 = lnext(p1); } /* |