Reimplement the linked list data structure used throughout the backend.

In the past, we used a 'Lispy' linked list implementation: a "list" was
merely a pointer to the head node of the list. The problem with that
design is that it makes lappend() and length() linear time. This patch
fixes that problem (and others) by maintaining a count of the list
length and a pointer to the tail node along with each head node pointer.
A "list" is now a pointer to a structure containing some meta-data
about the list; the head and tail pointers in that structure refer
to ListCell structures that maintain the actual linked list of nodes.

The function names of the list API have also been changed to, I hope,
be more logically consistent. By default, the old function names are
still available; they will be disabled-by-default once the rest of
the tree has been updated to use the new API names.

1 files changed, 20 insertions, 24 deletions

diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index e2f3d4aa813..3658a00ea21 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994-5, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/explain.c,v 1.120 2004/04/01 21:28:44 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/explain.c,v 1.121 2004/05/26 04:41:10 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -72,7 +72,7 @@ ExplainQuery(ExplainStmt *stmt, DestReceiver *dest)
 	Query	   *query = stmt->query;
 	TupOutputState *tstate;
 	List	   *rewritten;
-	List	   *l;
+	ListCell   *l;
 
 	/* prepare for projection of tuples */
 	tstate = begin_tup_output_tupdesc(dest, ExplainResultDesc(stmt));
@@ -104,7 +104,7 @@ ExplainQuery(ExplainStmt *stmt, DestReceiver *dest)
 			{
 				ExplainOneQuery(lfirst(l), stmt, tstate);
 				/* put a blank line between plans */
-				if (lnext(l) != NIL)
+				if (lnext(l) != NULL)
 					do_text_output_oneline(tstate, "");
 			}
 		}
@@ -156,9 +156,9 @@ ExplainOneQuery(Query *query, ExplainStmt *stmt, TupOutputState *tstate)
 			/* Still need to rewrite cursor command */
 			Assert(query->commandType == CMD_SELECT);
 			rewritten = QueryRewrite(query);
-			if (length(rewritten) != 1)
+			if (list_length(rewritten) != 1)
 				elog(ERROR, "unexpected rewrite result");
-			query = (Query *) lfirst(rewritten);
+			query = (Query *) linitial(rewritten);
 			Assert(query->commandType == CMD_SELECT);
 			/* do not actually execute the underlying query! */
 			stmt->analyze = false;
@@ -317,7 +317,7 @@ explain_outNode(StringInfo str,
 				Plan *outer_plan,
 				int indent, ExplainState *es)
 {
-	List	   *l;
+	ListCell	*l;
 	char	   *pname;
 	int			i;
 
@@ -491,7 +491,7 @@ explain_outNode(StringInfo str,
 			{
 				Relation	relation;
 
-				relation = index_open(lfirsto(l));
+				relation = index_open(lfirst_oid(l));
 				appendStringInfo(str, "%s%s",
 								 (++i > 1) ? ", " : "",
 					quote_identifier(RelationGetRelationName(relation)));
@@ -699,7 +699,7 @@ explain_outNode(StringInfo str,
 	if (plan->initPlan)
 	{
 		List	   *saved_rtable = es->rtable;
-		List	   *lst;
+		ListCell   *lst;
 
 		for (i = 0; i < indent; i++)
 			appendStringInfo(str, "  ");
@@ -749,7 +749,7 @@ explain_outNode(StringInfo str,
 	{
 		Append	   *appendplan = (Append *) plan;
 		AppendState *appendstate = (AppendState *) planstate;
-		List	   *lst;
+		ListCell   *lst;
 		int			j;
 
 		j = 0;
@@ -797,7 +797,7 @@ explain_outNode(StringInfo str,
 	if (planstate->subPlan)
 	{
 		List	   *saved_rtable = es->rtable;
-		List	   *lst;
+		ListCell   *lst;
 
 		for (i = 0; i < indent; i++)
 			appendStringInfo(str, "  ");
@@ -839,11 +839,8 @@ show_scan_qual(List *qual, bool is_or_qual, const char *qlabel,
 	/* No work if empty qual */
 	if (qual == NIL)
 		return;
-	if (is_or_qual)
-	{
-		if (lfirst(qual) == NIL && lnext(qual) == NIL)
-			return;
-	}
+	if (is_or_qual && list_length(qual) == 1 && linitial(qual) == NIL)
+		return;
 
 	/* Fix qual --- indexqual requires different processing */
 	if (is_or_qual)
@@ -852,7 +849,7 @@ show_scan_qual(List *qual, bool is_or_qual, const char *qlabel,
 		node = (Node *) make_ands_explicit(qual);
 
 	/* Generate deparse context */
-	Assert(scanrelid > 0 && scanrelid <= length(es->rtable));
+	Assert(scanrelid > 0 && scanrelid <= list_length(es->rtable));
 	rte = rt_fetch(scanrelid, es->rtable);
 	scancontext = deparse_context_for_rte(rte);
 
@@ -984,7 +981,7 @@ show_sort_keys(List *tlist, int nkeys, AttrNumber *keycols,
 		context = deparse_context_for_plan(0, NULL,
 										   0, NULL,
 										   es->rtable);
-		useprefix = length(es->rtable) > 1;
+		useprefix = list_length(es->rtable) > 1;
 	}
 	bms_free(varnos);
 
@@ -1017,17 +1014,16 @@ make_ors_ands_explicit(List *orclauses)
 {
 	if (orclauses == NIL)
 		return NULL;			/* probably can't happen */
-	else if (lnext(orclauses) == NIL)
-		return (Node *) make_ands_explicit(lfirst(orclauses));
+	else if (list_length(orclauses) == 1)
+		return (Node *) make_ands_explicit(linitial(orclauses));
 	else
 	{
-		FastList	args;
-		List	   *orptr;
+		List	   *args = NIL;
+		ListCell   *orptr;
 
-		FastListInit(&args);
 		foreach(orptr, orclauses)
-			FastAppend(&args, make_ands_explicit(lfirst(orptr)));
+			args = lappend(args, make_ands_explicit(lfirst(orptr)));
 
-		return (Node *) make_orclause(FastListValue(&args));
+		return (Node *) make_orclause(args);
 	}
 }