From 8dc08e26b4953332c91d17c63c119669ab13bc6c Mon Sep 17 00:00:00 2001
From: ian <141902143+yumosx@users.noreply.github.com>
Date: Tue, 18 Mar 2025 23:38:17 +0800
Subject: [PATCH] attribute: preallocate map in NewAllowKeysFilter and
 NewDenyKeysFilter (#6455)

preallocate map in `NewAllowKeysFilter` and `NewDenyKeysFilter` to avoid
necessary allocations
---
 CHANGELOG.md        | 1 +
 attribute/filter.go | 4 ++--
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9653e7d28..609c68cfc 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -17,6 +17,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - ⚠️ Update `github.com/prometheus/client_golang` to `v1.21.1`, which changes the `NameValidationScheme` to `UTF8Validation`.
   This allows metrics names to keep original delimiters (e.g. `.`), rather than replacing with underscores.
   This can be reverted by setting `github.com/prometheus/common/model.NameValidationScheme` to `LegacyValidation` in `github.com/prometheus/common/model`. (#6433)
+- Initialize map with `len(keys)` in `NewAllowKeysFilter` and `NewDenyKeysFilter` to avoid unnecessary allocations in `go.opentelemetry.io/otel/attribute`. (#6455)
 
 ### Fixes
 
diff --git a/attribute/filter.go b/attribute/filter.go
index be9cd922d..3eeaa5d44 100644
--- a/attribute/filter.go
+++ b/attribute/filter.go
@@ -19,7 +19,7 @@ func NewAllowKeysFilter(keys ...Key) Filter {
 		return func(kv KeyValue) bool { return false }
 	}
 
-	allowed := make(map[Key]struct{})
+	allowed := make(map[Key]struct{}, len(keys))
 	for _, k := range keys {
 		allowed[k] = struct{}{}
 	}
@@ -38,7 +38,7 @@ func NewDenyKeysFilter(keys ...Key) Filter {
 		return func(kv KeyValue) bool { return true }
 	}
 
-	forbid := make(map[Key]struct{})
+	forbid := make(map[Key]struct{}, len(keys))
 	for _, k := range keys {
 		forbid[k] = struct{}{}
 	}