From 0864fbe1fbff2000050afaee19bd50f34d2c714f Mon Sep 17 00:00:00 2001
From: Julien Rouhaud <julien.rouhaud@free.fr>
Date: Fri, 22 Jan 2021 17:49:48 +0800
Subject: [PATCH] Add a new hypo_get_index() function.

This will be helpful in a following patch.  The immediate effect is to fix a
long standing small performance issue, as hypo_explain_get_index_name_hook
didn't stop its loop once it found a matching entry.
---
 hypopg_index.c         | 43 +++++++++++++++++++++++-------------------
 include/hypopg_index.h |  1 +
 2 files changed, 25 insertions(+), 19 deletions(-)

diff --git a/hypopg_index.c b/hypopg_index.c
index d79648c..12d1dc5 100644
--- a/hypopg_index.c
+++ b/hypopg_index.c
@@ -1116,36 +1116,41 @@ hypo_injectHypotheticalIndex(PlannerInfo *root,
 	rel->indexlist = lcons(index, rel->indexlist);
 }
 
-/* Return the hypothetical index name is indexId is ours, NULL otherwise, as
+/*
+ * Return the stored hypothetical index for a given oid if any, NULL otherwise
+ */
+hypoIndex *
+hypo_get_index(Oid indexId)
+{
+	ListCell   *lc;
+
+	foreach(lc, hypoIndexes)
+	{
+		hypoIndex  *entry = (hypoIndex *) lfirst(lc);
+
+		if (entry->oid == indexId)
+			return entry;
+	}
+
+	return NULL;
+}
+
+/* Return the hypothetical index name ifs indexId is ours, NULL otherwise, as
  * this is what explain_get_index_name expects to continue his job.
  */
 const char *
 hypo_explain_get_index_name_hook(Oid indexId)
 {
-	char	   *ret = NULL;
-
 	if (isExplain)
 	{
-		/*
-		 * we're in an explain-only command. Return the name of the
-		 * hypothetical index name if it's one of ours, otherwise return NULL
-		 */
-		ListCell   *lc;
+		hypoIndex  *index = NULL;
 
-		foreach(lc, hypoIndexes)
-		{
-			hypoIndex  *entry = (hypoIndex *) lfirst(lc);
+		index = hypo_get_index(indexId);
 
-			if (entry->oid == indexId)
-			{
-				ret = entry->indexname;
-			}
-		}
+		if (index)
+			return index->indexname;
 	}
 
-	if (ret)
-		return ret;
-
 	if (prev_explain_get_index_name_hook)
 		return prev_explain_get_index_name_hook(indexId);
 
diff --git a/include/hypopg_index.h b/include/hypopg_index.h
index 323cadc..3ffb637 100644
--- a/include/hypopg_index.h
+++ b/include/hypopg_index.h
@@ -120,6 +120,7 @@ PGDLLEXPORT Datum hypopg_get_indexdef(PG_FUNCTION_ARGS);
 PGDLLEXPORT Datum hypopg_reset_index(PG_FUNCTION_ARGS);
 
 extern explain_get_index_name_hook_type prev_explain_get_index_name_hook;
+hypoIndex *hypo_get_index(Oid indexId);
 const char *hypo_explain_get_index_name_hook(Oid indexId);
 
 void		hypo_injectHypotheticalIndex(PlannerInfo *root,