reduce gas costs by 10x for transient store operations (cosmos#8790)

* reduce gas costs by 10x for transient store operations

* fix TestTransientGasConfig for ReadCostFlat

* added changelog entry

* fix changelog

* fix changelog

Co-authored-by: Alessio Treglia <alessio@tendermint.com>

CHANGELOG.md

@@ -68,6 +68,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 * (x/gov) [\#7733](https://github.com/cosmos/cosmos-sdk/pull/7733) ADR 037 Implementation: Governance Split Votes
 * (x/bank) [\#8656](https://github.com/cosmos/cosmos-sdk/pull/8656) balance and supply are now correctly tracked via `coin_spent`, `coin_received`, `coinbase` and `burn` events.
 * (x/bank) [\#8517](https://github.com/cosmos/cosmos-sdk/pull/8517) Supply is now stored and tracked as `sdk.Coins`
+* (store) [\#8790](https://github.com/cosmos/cosmos-sdk/pull/8790) Reduce gas costs by 10x for transient store operations.
 
 ### Improvements
 

store/types/gas.go

@@ -176,6 +176,13 @@ func KVGasConfig() GasConfig {
 
 // TransientGasConfig returns a default gas config for TransientStores.
 func TransientGasConfig() GasConfig {
-	// TODO: define gasconfig for transient stores
-	return KVGasConfig()
+	return GasConfig{
+		HasCost:          100,
+		DeleteCost:       100,
+		ReadCostFlat:     100,
+		ReadCostPerByte:  0,
+		WriteCostFlat:    200,
+		WriteCostPerByte: 3,
+		IterNextCostFlat: 3,
+	}
 }

store/types/gas_test.go

@@ -93,12 +93,12 @@ func TestTransientGasConfig(t *testing.T) {
 	t.Parallel()
 	config := TransientGasConfig()
 	require.Equal(t, config, GasConfig{
-		HasCost:          1000,
-		DeleteCost:       1000,
-		ReadCostFlat:     1000,
-		ReadCostPerByte:  3,
-		WriteCostFlat:    2000,
-		WriteCostPerByte: 30,
-		IterNextCostFlat: 30,
+		HasCost:          100,
+		DeleteCost:       100,
+		ReadCostFlat:     100,
+		ReadCostPerByte:  0,
+		WriteCostFlat:    200,
+		WriteCostPerByte: 3,
+		IterNextCostFlat: 3,
 	})
 }