From 67b2ceea01576933a1dc881ef6a65403e03483ee Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Mon, 28 Sep 2020 20:32:53 -0400 Subject: Add for_each_from, to simplify loops starting from non-first list cells. We have a dozen or so places that need to iterate over all but the first cell of a List. Prior to v13 this was typically written as for_each_cell(lc, lnext(list_head(list))) Commit 1cff1b95a changed these to for_each_cell(lc, list, list_second_cell(list)) This patch introduces a new macro for_each_from() which expresses the start point as a list index, allowing these to be written as for_each_from(lc, list, 1) This is marginally more efficient, since ForEachState.i can be initialized directly instead of backing into it from a ListCell address. It also seems clearer and less typo-prone. Some of the remaining uses of for_each_cell() look like they could profitably be changed to for_each_from(), but here I confined myself to changing uses of list_second_cell(). Also, fix for_each_cell_setup() and for_both_cell_setup() to const-ify their arguments; that's a simple oversight in 1cff1b95a. Back-patch into v13, on the grounds that (1) the const-ification is a minor bug fix, and (2) it's better for back-patching purposes if we only have two ways to write these loops rather than three. In HEAD, also remove list_third_cell() and list_fourth_cell(), which were also introduced in 1cff1b95a, and are unused as of cc99baa43. It seems unlikely that any third-party code would have started to use them already; anyone who has can be directed to list_nth_cell instead. Discussion: https://postgr.es/m/CAApHDvpo1zj9KhEpU2cCRZfSM3Q6XGdhzuAS2v79PH7WJBkYVA@mail.gmail.com --- src/backend/utils/adt/ruleutils.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) (limited to 'src/backend/utils/adt/ruleutils.c') diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c index 076c3c019ff..9db584169fc 100644 --- a/src/backend/utils/adt/ruleutils.c +++ b/src/backend/utils/adt/ruleutils.c @@ -8123,7 +8123,7 @@ get_rule_expr(Node *node, deparse_context *context, { BoolExpr *expr = (BoolExpr *) node; Node *first_arg = linitial(expr->args); - ListCell *arg = list_second_cell(expr->args); + ListCell *arg; switch (expr->boolop) { @@ -8132,12 +8132,11 @@ get_rule_expr(Node *node, deparse_context *context, appendStringInfoChar(buf, '('); get_rule_expr_paren(first_arg, context, false, node); - while (arg) + for_each_from(arg, expr->args, 1) { appendStringInfoString(buf, " AND "); get_rule_expr_paren((Node *) lfirst(arg), context, false, node); - arg = lnext(expr->args, arg); } if (!PRETTY_PAREN(context)) appendStringInfoChar(buf, ')'); @@ -8148,12 +8147,11 @@ get_rule_expr(Node *node, deparse_context *context, appendStringInfoChar(buf, '('); get_rule_expr_paren(first_arg, context, false, node); - while (arg) + for_each_from(arg, expr->args, 1) { appendStringInfoString(buf, " OR "); get_rule_expr_paren((Node *) lfirst(arg), context, false, node); - arg = lnext(expr->args, arg); } if (!PRETTY_PAREN(context)) appendStringInfoChar(buf, ')'); -- cgit v1.2.3