Revert "rpc: performance fix for getProgramAccounts (solana-labs#19941)"

This reverts commit 05415ce.

rpc/src/rpc.rs

@@ -350,15 +350,18 @@ 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())?;
 
-        let accounts = pubkeys
-            .into_iter()
-            .map(|pubkey| get_encoded_account(&bank, &pubkey, encoding, config.data_slice))
-            .collect::<Result<Vec<_>>>()?;
+        for pubkey in pubkeys {
+            let response_account =
+                get_encoded_account(&bank, &pubkey, encoding, config.data_slice)?;
+            accounts.push(response_account)
+        }
         Ok(new_response(&bank, accounts))
     }
 
@@ -392,21 +395,19 @@ impl JsonRpcRequestProcessor {
                 self.get_filtered_program_accounts(&bank, program_id, filters)?
             }
         };
-        let result = if program_id == &spl_token_id_v2_0()
-            && encoding == UiAccountEncoding::JsonParsed
-        {
-            get_parsed_token_accounts(bank.clone(), keyed_accounts.into_iter()).collect()
-        } else {
-            keyed_accounts
-                .into_iter()
-                .map(|(pubkey, account)| {
-                    Ok(RpcKeyedAccount {
+        let result =
+            if program_id == &spl_token_id_v2_0() && encoding == UiAccountEncoding::JsonParsed {
+                get_parsed_token_accounts(bank.clone(), keyed_accounts.into_iter()).collect()
+            } else {
+                let mut encoded_accounts = vec![];
+                for (pubkey, account) in keyed_accounts {
+                    encoded_accounts.push(RpcKeyedAccount {
                         pubkey: pubkey.to_string(),
                         account: encode_account(&account, &pubkey, encoding, data_slice_config)?,
-                    })
-                })
-                .collect::<Result<Vec<_>>>()?
-        };
+                    });
+                }
+                encoded_accounts
+            };
         Ok(result).map(|result| match with_context {
             true => OptionalContext::Context(new_response(&bank, result)),
             false => OptionalContext::NoContext(result),
@@ -2825,10 +2826,10 @@ pub mod rpc_accounts {
                     max_multiple_accounts
                 )));
             }
-            let pubkeys = pubkey_strs
-                .into_iter()
-                .map(|pubkey_str| verify_pubkey(&pubkey_str))
-                .collect::<Result<Vec<_>>>()?;
+            let mut pubkeys: Vec<Pubkey> = vec![];
+            for pubkey_str in pubkey_strs {
+                pubkeys.push(verify_pubkey(&pubkey_str)?);
+            }
             meta.get_multiple_accounts(pubkeys, config)
         }