From 5904e4ac79d3b40182dc39945c093cb77676b87f Mon Sep 17 00:00:00 2001
From: Dhia Ayachi <dhia@hashicorp.com>
Date: Thu, 23 Sep 2021 11:06:23 -0400
Subject: [PATCH] Refactor table index (#11131)

* convert tableIndex to use the new pattern

* make `indexFromString` available for oss as well

* refactor `indexUpdateMaxTxn`
---
 agent/consul/state/schema.go      | 33 ++++++++++++++++++++++++++++---
 agent/consul/state/state_store.go | 21 +++++++++++---------
 2 files changed, 42 insertions(+), 12 deletions(-)

diff --git a/agent/consul/state/schema.go b/agent/consul/state/schema.go
index cecb2a2a34..bca4eec01b 100644
--- a/agent/consul/state/schema.go
+++ b/agent/consul/state/schema.go
@@ -2,6 +2,7 @@ package state
 
 import (
 	"fmt"
+	"strings"
 
 	"github.com/hashicorp/go-memdb"
 )
@@ -75,11 +76,37 @@ func indexTableSchema() *memdb.TableSchema {
 				Name:         indexID,
 				AllowMissing: false,
 				Unique:       true,
-				Indexer: &memdb.StringFieldIndex{
-					Field:     "Key",
-					Lowercase: true,
+				Indexer: indexerSingle{
+					readIndex:  indexFromString,
+					writeIndex: indexNameFromIndexEntry,
 				},
 			},
 		},
 	}
 }
+
+func indexNameFromIndexEntry(raw interface{}) ([]byte, error) {
+	p, ok := raw.(*IndexEntry)
+	if !ok {
+		return nil, fmt.Errorf("unexpected type %T for IndexEntry index", raw)
+	}
+
+	if p.Key == "" {
+		return nil, errMissingValueForIndex
+	}
+
+	var b indexBuilder
+	b.String(strings.ToLower(p.Key))
+	return b.Bytes(), nil
+}
+
+func indexFromString(raw interface{}) ([]byte, error) {
+	q, ok := raw.(string)
+	if !ok {
+		return nil, fmt.Errorf("unexpected type %T for string prefix query", raw)
+	}
+
+	var b indexBuilder
+	b.String(strings.ToLower(q))
+	return b.Bytes(), nil
+}
diff --git a/agent/consul/state/state_store.go b/agent/consul/state/state_store.go
index a0a26243e8..fdfcb16fcf 100644
--- a/agent/consul/state/state_store.go
+++ b/agent/consul/state/state_store.go
@@ -295,17 +295,20 @@ func indexUpdateMaxTxn(tx WriteTxn, idx uint64, table string) error {
 		return fmt.Errorf("failed to retrieve existing index: %s", err)
 	}
 
-	// Always take the first update, otherwise do the > check.
-	if ti == nil {
-		if err := tx.Insert(tableIndex, &IndexEntry{table, idx}); err != nil {
-			return fmt.Errorf("failed updating index %s", err)
+	// if this is an update check the idx
+	if ti != nil {
+		cur, ok := ti.(*IndexEntry)
+		if !ok {
+			return fmt.Errorf("failed updating index %T need to be `*IndexEntry`", ti)
 		}
-		return nil
-	}
-	if cur, ok := ti.(*IndexEntry); ok && idx > cur.Value {
-		if err := tx.Insert(tableIndex, &IndexEntry{table, idx}); err != nil {
-			return fmt.Errorf("failed updating index %s", err)
+		// Stored index is newer, don't insert the index
+		if idx <= cur.Value {
+			return nil
 		}
 	}
+
+	if err := tx.Insert(tableIndex, &IndexEntry{table, idx}); err != nil {
+		return fmt.Errorf("failed updating index %s", err)
+	}
 	return nil
 }