From 1b013a94f7c0b0e06ecc7f096db9a35f91321e5d Mon Sep 17 00:00:00 2001
From: Andrew Kane <andrew@ankane.org>
Date: Mon, 10 Apr 2023 21:28:24 -0700
Subject: [PATCH] Added notice when index created with little data [skip ci]

---
 CHANGELOG.md   |  4 ++++
 src/ivfbuild.c | 10 ++++++++++
 2 files changed, 14 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index dff48c5..23865e0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 0.4.2 (unreleased)
+
+- Added notice when index created with little data
+
 ## 0.4.1 (2023-03-21)
 
 - Improved performance of cosine distance
diff --git a/src/ivfbuild.c b/src/ivfbuild.c
index 9a3697c..854207a 100644
--- a/src/ivfbuild.c
+++ b/src/ivfbuild.c
@@ -431,8 +431,18 @@ ComputeCenters(IvfflatBuildState * buildstate)
 	/* TODO Ensure within maintenance_work_mem */
 	buildstate->samples = VectorArrayInit(numSamples, buildstate->dimensions);
 	if (buildstate->heap != NULL)
+	{
 		SampleRows(buildstate);
 
+		if (buildstate->samples->length < buildstate->lists)
+		{
+			ereport(NOTICE,
+					(errmsg("index created with little data"),
+					 errdetail("this will cause poor recall"),
+					 errhint("drop the index until the table has more data")));
+		}
+	}
+
 	/* Calculate centers */
 	IvfflatBench("k-means", IvfflatKmeans(buildstate->index, buildstate->samples, buildstate->centers));