From da7185e2ede7fdf7656fdf3eda2a4255328991aa Mon Sep 17 00:00:00 2001
From: "mergify[bot]" <37929162+mergify[bot]@users.noreply.github.com>
Date: Thu, 16 Sep 2021 23:09:11 +0000
Subject: [PATCH] rpc: performance fix for getProgramAccounts (backport #19941)
 (#19949)

* rpc: performance fix for getProgramAccounts (#19941)

* rpc: performance fix for getProgramAccounts

The accounts were gradually pushed into a vector, which produced
significant slowdowns for very large responses.

* rpc: rewrite loops using iterators

Co-authored-by: Christian Kamm <ckamm@delightful-solutions.de>
(cherry picked from commit f1bbf1d8b09256b4baa4753c27b61dae4e7908a7)

# Conflicts:
#	core/src/rpc.rs

* fix conflicts

* Fix conflicts

Co-authored-by: Christian Kamm <mail@ckamm.de>
Co-authored-by: Justin Starry <justin@solana.com>
Co-authored-by: Tyera Eulberg <tyera@solana.com>
---
 core/src/rpc.rs | 41 ++++++++++++++++++++---------------------
 1 file changed, 20 insertions(+), 21 deletions(-)

diff --git a/core/src/rpc.rs b/core/src/rpc.rs
index 8c83ea6911f76c..b6532064359e30 100644
--- a/core/src/rpc.rs
+++ b/core/src/rpc.rs
@@ -328,18 +328,15 @@ impl JsonRpcRequestProcessor {
         pubkeys: Vec<Pubkey>,
         config: Option<RpcAccountInfoConfig>,
     ) -> Result<RpcResponse<Vec<Option<UiAccount>>>> {
-        let mut accounts: Vec<Option<UiAccount>> = vec![];
-
         let config = config.unwrap_or_default();
         let bank = self.bank(config.commitment);
         let encoding = config.encoding.unwrap_or(UiAccountEncoding::Base64);
         check_slice_and_encoding(&encoding, config.data_slice.is_some())?;
 
-        for pubkey in pubkeys {
-            let response_account =
-                get_encoded_account(&bank, &pubkey, encoding, config.data_slice)?;
-            accounts.push(response_account)
-        }
+        let accounts = pubkeys
+            .into_iter()
+            .map(|pubkey| get_encoded_account(&bank, &pubkey, encoding, config.data_slice))
+            .collect::<Result<Vec<_>>>()?;
         Ok(new_response(&bank, accounts))
     }
 
@@ -379,17 +376,19 @@ impl JsonRpcRequestProcessor {
             } else {
                 keyed_accounts
                     .into_iter()
-                    .map(|(pubkey, account)| RpcKeyedAccount {
-                        pubkey: pubkey.to_string(),
-                        account: UiAccount::encode(
-                            &pubkey,
-                            &account,
-                            encoding,
-                            None,
-                            data_slice_config,
-                        ),
+                    .map(|(pubkey, account)| {
+                        Ok(RpcKeyedAccount {
+                            pubkey: pubkey.to_string(),
+                            account: UiAccount::encode(
+                                &pubkey,
+                                &account,
+                                encoding,
+                                None,
+                                data_slice_config,
+                            ),
+                        })
                     })
-                    .collect()
+                    .collect::<Result<Vec<_>>>()?
             };
         Ok(result).map(|result| match with_context {
             true => OptionalContext::Context(new_response(&bank, result)),
@@ -2804,10 +2803,10 @@ pub mod rpc_full {
                     max_multiple_accounts
                 )));
             }
-            let mut pubkeys: Vec<Pubkey> = vec![];
-            for pubkey_str in pubkey_strs {
-                pubkeys.push(verify_pubkey(&pubkey_str)?);
-            }
+            let pubkeys = pubkey_strs
+                .into_iter()
+                .map(|pubkey_str| verify_pubkey(&pubkey_str))
+                .collect::<Result<Vec<_>>>()?;
             meta.get_multiple_accounts(pubkeys, config)
         }