From c0aeb0e65e23c1e97f1175c3b4305aca183d97b1 Mon Sep 17 00:00:00 2001
From: Jan Nidzwetzki <jan@timescale.com>
Date: Mon, 15 May 2023 17:00:12 +0200
Subject: [PATCH] Reworked path handling

---
 src/planner/expand_hypertable.c               |   2 +-
 .../decompress_chunk_vector.c                 | 101 ++++++++++++++----
 2 files changed, 84 insertions(+), 19 deletions(-)

diff --git a/src/planner/expand_hypertable.c b/src/planner/expand_hypertable.c
index 9c859acea34..a9d3173a346 100644
--- a/src/planner/expand_hypertable.c
+++ b/src/planner/expand_hypertable.c
@@ -1420,7 +1420,7 @@ ts_plan_expand_hypertable_chunks(Hypertable *ht, PlannerInfo *root, RelOptInfo *
 		 !has_partialize_function((Node *) root->parse->targetList, TS_DO_NOT_FIX_AGGSPLIT)) ||
 		hypertable_is_distributed(ht))
 	{
-		if(! hypertable_is_distributed(ht))
+		if (!hypertable_is_distributed(ht))
 			enable_partitionwise_aggregate = true;
 
 		build_hypertable_partition_info(ht, root, rel, list_length(inh_oids));
diff --git a/tsl/src/nodes/decompress_chunk_vector/decompress_chunk_vector.c b/tsl/src/nodes/decompress_chunk_vector/decompress_chunk_vector.c
index ecde7c441dd..5e5c93a09e5 100644
--- a/tsl/src/nodes/decompress_chunk_vector/decompress_chunk_vector.c
+++ b/tsl/src/nodes/decompress_chunk_vector/decompress_chunk_vector.c
@@ -32,22 +32,101 @@
 #include "nodes/decompress_chunk_vector/decompress_chunk_vector.h"
 #include "utils.h"
 
+/* Check if we can vectorize the given path */
+static bool
+is_vectorizable_agg_path(Path *path)
+{
+	if (!IsA(path, AggPath))
+		return false;
+
+	AggPath *agg_path = castNode(AggPath, path);
+
+	bool is_plain_agg = (agg_path->aggstrategy == AGG_PLAIN);
+	if (!is_plain_agg)
+		return false;
+
+	bool is_decompress_chunk = ts_is_decompress_chunk_path(agg_path->subpath);
+	if (!is_decompress_chunk)
+		return false;
+
+	/* We currently handle only one agg function per node */
+	if (list_length(agg_path->path.pathtarget->exprs) != 1)
+		return false;
+
+	/* Only sum on int 4 is supported at the moment */
+	Node *expr_node = linitial(agg_path->path.pathtarget->exprs);
+	if (!IsA(expr_node, Aggref))
+		return false;
+
+	Aggref *aggref = castNode(Aggref, expr_node);
+
+	if (aggref->aggfnoid != F_SUM_INT4)
+		return false;
+
+	return true;
+}
+
+/* Generate cheaper path with our vector node */
 static void
-handle_agg_sub_path(Path *agg_sub_path)
+add_vector_path_append(AppendPath *append_path, Path *path)
+{
+	Assert(path != NULL);
+	Assert(IsA(path, AggPath));
+
+	AggPath *agg_path = castNode(AggPath, path);
+}
+
+static void
+add_vector_path_merge_append(MergeAppendPath *merge_append_path, Path *path)
 {
-	List *subpaths = NIL;
+	Assert(path != NULL);
+	Assert(IsA(path, AggPath));
 
+	AggPath *agg_path = castNode(AggPath, path);
+}
+
+static void
+handle_agg_sub_path(Path *agg_sub_path)
+{
 	Assert(agg_sub_path != NULL);
 
 	if (IsA(agg_sub_path, AppendPath))
 	{
 		AppendPath *append_path = castNode(AppendPath, agg_sub_path);
-		subpaths = append_path->subpaths;
+		List *subpaths = append_path->subpaths;
+
+		/* No subpaths available */
+		if (list_length(subpaths) < 1)
+			return;
+
+		ListCell *lc;
+
+		/* Check if subpath can be vectorized */
+		foreach (lc, subpaths)
+		{
+			Path *sub_path = lfirst(lc);
+			if (is_vectorizable_agg_path(sub_path))
+				add_vector_path_append(append_path, sub_path);
+		}
 	}
 	else if (IsA(agg_sub_path, MergeAppendPath))
 	{
 		MergeAppendPath *merge_append_path = castNode(MergeAppendPath, agg_sub_path);
-		subpaths = merge_append_path->subpaths;
+		List *subpaths = merge_append_path->subpaths;
+
+		/* No subpaths available */
+		if (list_length(subpaths) < 1)
+			return;
+
+		ListCell *lc;
+
+		/* Check if subpath can be vectorized */
+		foreach (lc, subpaths)
+		{
+			Path *sub_path = lfirst(lc);
+			if (is_vectorizable_agg_path(sub_path))
+				add_vector_path_merge_append(merge_append_path, sub_path);
+		}
 	}
 	else if (IsA(agg_sub_path, GatherPath))
 	{
@@ -59,20 +138,6 @@ handle_agg_sub_path(Path *agg_sub_path)
 		if (gather_path->subpath != NULL)
 			handle_agg_sub_path(gather_path->subpath);
 	}
-	else
-	{
-		/* Unsupported sub path */
-		return;
-	}
-
-	/* No subpaths available */
-	if (list_length(subpaths) < 1)
-		return;
-
-	// Get Paths from Append and MergeAppendPath
-	// Check for disabled optimizations (ChunkAppend)
-	// Check Paths for partial aggegate on top of ts_is_decompress_chunk_path
-	// Replace with a DecompressChunkVectorPath
 }
 
 /*