From 9cddee94f80fb72539a9c16935274f9a1e255f05 Mon Sep 17 00:00:00 2001
From: Vincent Bernat <vincent@bernat.ch>
Date: Mon, 21 Nov 2022 18:38:50 +0100
Subject: [PATCH] console: fix selection of aggregate table on impossible
 resolution

When requesting a too small resolution for data that are too far in the
past, prefer to select a table with data than a table without.
Previously, the resolution was a hard requirement.
---
 console/clickhouse.go             | 24 +++++++++++++-----------
 console/clickhouse_test.go        | 15 +++++++++++++++
 console/data/docs/99-changelog.md |  1 +
 3 files changed, 29 insertions(+), 11 deletions(-)

diff --git a/console/clickhouse.go b/console/clickhouse.go
index 6699ba9d..a30e6a2b 100644
--- a/console/clickhouse.go
+++ b/console/clickhouse.go
@@ -8,6 +8,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"sort"
 	"strings"
 	"text/template"
 	"time"
@@ -220,10 +221,12 @@ func (c *Component) getBestTable(start time.Time, targetInterval time.Duration)
 		// We can use the consolidated data. The first
 		// criteria is to find the tables matching the time
 		// criteria.
+		fmt.Println(c.flowsTables)
 		candidates := []int{}
 		for idx, table := range c.flowsTables {
 			if start.After(table.Oldest.Add(table.Resolution)) {
 				candidates = append(candidates, idx)
+				fmt.Println(candidates)
 			}
 		}
 		if len(candidates) == 0 {
@@ -245,20 +248,19 @@ func (c *Component) getBestTable(start time.Time, targetInterval time.Duration)
 				}
 			}
 		}
-		if len(candidates) > 1 {
-			// Use interval to find the best one
-			best := 0
-			for _, idx := range candidates {
-				if c.flowsTables[idx].Resolution > targetInterval {
-					continue
-				}
-				if c.flowsTables[idx].Resolution > c.flowsTables[best].Resolution {
-					best = idx
-				}
+		sort.Slice(candidates, func(i, j int) bool {
+			return c.flowsTables[candidates[i]].Resolution < c.flowsTables[candidates[j]].Resolution
+		})
+		// If possible, use the first resolution before the target interval
+		for len(candidates) > 1 {
+			if c.flowsTables[candidates[1]].Resolution < targetInterval {
+				candidates = candidates[1:]
+			} else {
+				break
 			}
-			candidates = []int{best}
 		}
 		table = c.flowsTables[candidates[0]].Name
+		fmt.Println(table)
 		computedInterval = c.flowsTables[candidates[0]].Resolution
 	}
 	if computedInterval < time.Second {
diff --git a/console/clickhouse_test.go b/console/clickhouse_test.go
index 59d137fc..2b95d731 100644
--- a/console/clickhouse_test.go
+++ b/console/clickhouse_test.go
@@ -270,6 +270,21 @@ func TestFinalizeQuery(t *testing.T) {
 				Points: 720,
 			},
 			Expected: `toStartOfInterval(TimeReceived + INTERVAL 50 second, INTERVAL 120 second) - INTERVAL 50 second`,
+		}, {
+			Description: "Small interval outside main table expiration",
+			Query:       "SELECT InIfProvider FROM {{ .Table }}",
+			Tables: []flowsTable{
+				{"flows", time.Duration(0), time.Date(2022, 11, 06, 12, 0, 0, 0, time.UTC)},
+				{"flows_1h0m0s", time.Hour, time.Date(2022, 04, 25, 18, 0, 0, 0, time.UTC)},
+				{"flows_1m0s", time.Minute, time.Date(2022, 11, 14, 12, 0, 0, 0, time.UTC)},
+				{"flows_5m0s", 5 * time.Minute, time.Date(2022, 8, 23, 12, 0, 0, 0, time.UTC)},
+			},
+			Context: inputContext{
+				Start:  time.Date(2022, 10, 30, 1, 0, 0, 0, time.UTC),
+				End:    time.Date(2022, 10, 30, 12, 0, 0, 0, time.UTC),
+				Points: 200,
+			},
+			Expected: "SELECT InIfProvider FROM flows_5m0s",
 		},
 	}
 
diff --git a/console/data/docs/99-changelog.md b/console/data/docs/99-changelog.md
index 50775d7d..a86ff6ca 100644
--- a/console/data/docs/99-changelog.md
+++ b/console/data/docs/99-changelog.md
@@ -21,6 +21,7 @@ details.
 
 - 🩹 *inlet*: handle non-fatal BMP decoding errors more gracefully
 - 🩹 *inlet*: fix a small memory leak in BMP collector
+- 🩹 *console*: fix selection of the aggregate table to not get empty graphs
 - 🩹 *console*: use configured dimensions limit for “Visualize” tab
 - 🌱 *inlet*: optimize BMP collector (see above)
 - 🌱 *inlet*: replace LRU cache for classifiers by a time-based cache