From 297b3e03aa7e870949dc052b547f78d1f38ebdcf Mon Sep 17 00:00:00 2001
From: Dev Ojha <ValarDragon@users.noreply.github.com>
Date: Fri, 3 Sep 2021 12:46:09 -0400
Subject: [PATCH 1/2] Improve the speed of coins.String() (#30)

---
 types/coin.go | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/types/coin.go b/types/coin.go
index 3cfc58b7b3bb..facdd56a2206 100644
--- a/types/coin.go
+++ b/types/coin.go
@@ -34,7 +34,7 @@ func NewInt64Coin(denom string, amount int64) Coin {
 
 // String provides a human-readable representation of a coin
 func (coin Coin) String() string {
-	return fmt.Sprintf("%v%v", coin.Amount, coin.Denom)
+	return fmt.Sprintf("%v%s", coin.Amount, coin.Denom)
 }
 
 // Validate returns an error if the Coin has a negative amount or if
@@ -185,13 +185,18 @@ func (coins Coins) MarshalJSON() ([]byte, error) {
 func (coins Coins) String() string {
 	if len(coins) == 0 {
 		return ""
+	} else if len(coins) == 1 {
+		return coins[0].String()
 	}
 
-	out := ""
-	for _, coin := range coins {
-		out += fmt.Sprintf("%v,", coin.String())
+	// Build the string with a string builder
+	var out strings.Builder
+	for _, coin := range coins[:len(coins)-1] {
+		out.WriteString(coin.String())
+		out.WriteByte(',')
 	}
-	return out[:len(out)-1]
+	out.WriteString(coins[len(coins)-1].String())
+	return out.String()
 }
 
 // Validate checks that the Coins are sorted, have positive amount, with a valid and unique

From d09fd3e40b904127811791670d89cfb0c9af842f Mon Sep 17 00:00:00 2001
From: ValarDragon <dojha12@gmail.com>
Date: Fri, 3 Sep 2021 11:56:33 -0500
Subject: [PATCH 2/2] Update Changelog

---
 CHANGELOG.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0fb74788aaca..e17b6e8f4ae2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -86,6 +86,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 ### Improvements
 
+* (types) [\#10076](https://github.com/cosmos/cosmos-sdk/pull/10076) Significantly speedup and lower allocations for `Coins.String()`.
 * (x/bank) [\#10022](https://github.com/cosmos/cosmos-sdk/pull/10022) `BankKeeper.SendCoins` now takes less execution time.
 * (deps) [\#9956](https://github.com/cosmos/cosmos-sdk/pull/9956) Bump Tendermint to [v0.34.12](https://github.com/tendermint/tendermint/releases/tag/v0.34.12).
 * (cli) [\#9856](https://github.com/cosmos/cosmos-sdk/pull/9856) Overwrite `--sequence` and `--account-number` flags with default flag values when used with `offline=false` in `sign-batch` command.