From a4243a794d6eaad3f4773c2d88061b9346c96e7a Mon Sep 17 00:00:00 2001
From: Mykhailo Kremniov <mkremniov@gmail.com>
Date: Thu, 14 Nov 2024 15:40:29 +0200
Subject: [PATCH] Use Vec::with_capacity in certain places (from PR #1831)

---
 .../api-server-common/src/storage/impls/postgres/queries.rs   | 2 +-
 chainstate/src/detail/median_time.rs                          | 2 +-
 chainstate/test-framework/src/framework.rs                    | 4 ++--
 test-rpc-functions/src/rpc.rs                                 | 2 +-
 4 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/api-server/api-server-common/src/storage/impls/postgres/queries.rs b/api-server/api-server-common/src/storage/impls/postgres/queries.rs
index 38c21cf729..d66be8102d 100644
--- a/api-server/api-server-common/src/storage/impls/postgres/queries.rs
+++ b/api-server/api-server-common/src/storage/impls/postgres/queries.rs
@@ -306,7 +306,7 @@ impl<'a, 'b> QueryFromConnection<'a, 'b> {
             .await
             .map_err(|e| ApiServerStorageError::LowLevelStorageError(e.to_string()))?;
 
-        let mut transaction_ids = vec![];
+        let mut transaction_ids = Vec::with_capacity(rows.len());
 
         for row in &rows {
             let transaction_id: Vec<u8> = row.get(0);
diff --git a/chainstate/src/detail/median_time.rs b/chainstate/src/detail/median_time.rs
index 8b1989746a..7b28898ceb 100644
--- a/chainstate/src/detail/median_time.rs
+++ b/chainstate/src/detail/median_time.rs
@@ -82,7 +82,7 @@ mod test {
         initial_prev: Id<GenBlock>,
         initial_time: BlockTimestampInternalType,
     ) -> Vec<Block> {
-        let mut res = vec![];
+        let mut res = Vec::with_capacity(count);
         let mut prev = initial_prev;
         let mut time = initial_time;
         for _ in 0..count {
diff --git a/chainstate/test-framework/src/framework.rs b/chainstate/test-framework/src/framework.rs
index f603a77f67..e31ffcd228 100644
--- a/chainstate/test-framework/src/framework.rs
+++ b/chainstate/test-framework/src/framework.rs
@@ -220,7 +220,7 @@ impl TestFramework {
     ) -> Result<Vec<Id<GenBlock>>, ChainstateError> {
         let mut prev_block_id = *parent_block;
         let result = || -> Result<Vec<Id<GenBlock>>, ChainstateError> {
-            let mut ids = Vec::new();
+            let mut ids = Vec::with_capacity(blocks_count);
             for _ in 0..blocks_count {
                 let block = self
                     .make_block_builder()
@@ -251,7 +251,7 @@ impl TestFramework {
     ) -> Result<Vec<Id<GenBlock>>, ChainstateError> {
         let mut prev_block_id = *parent_block;
         let result = || -> Result<Vec<Id<GenBlock>>, ChainstateError> {
-            let mut ids = Vec::new();
+            let mut ids = Vec::with_capacity(blocks_count);
             let target_block_time = self.chain_config().target_block_spacing();
             for _ in 0..blocks_count {
                 self.progress_time_seconds_since_epoch(target_block_time.as_secs());
diff --git a/test-rpc-functions/src/rpc.rs b/test-rpc-functions/src/rpc.rs
index fcfa88fd8f..d5aa9ad89b 100644
--- a/test-rpc-functions/src/rpc.rs
+++ b/test-rpc-functions/src/rpc.rs
@@ -342,7 +342,7 @@ impl RpcTestFunctionsRpcServer for super::RpcTestFunctionsHandle {
         let coin_decimal_factor = 10u128.pow(coin_decimals as u32);
         let mut amount_to_spend = (amount_to_spend as u128) * coin_decimal_factor;
         let fee_per_tx = (fee_per_tx as u128) * coin_decimal_factor;
-        let mut transactions = vec![];
+        let mut transactions = Vec::with_capacity(num_transactions as usize);
         for _ in 0..num_transactions {
             let inputs =
                 vec![TxInput::from_utxo(OutPointSourceId::Transaction(input_tx_id), input_idx)];