validator option: accounts-db-skip-rewrites (#24504)

ledger-tool/src/main.rs

@@ -963,6 +963,13 @@ fn main() {
         .validator(is_slot)
         .takes_value(true)
         .help("Halt processing at the given slot");
+    let skip_rewrites_arg = Arg::with_name("accounts_db_skip_rewrites")
+        .long("accounts-db-skip-rewrites")
+        .help(
+            "Accounts that are rent exempt and have no changes are not rewritten. \
+                  This produces snapshots that older versions cannot read.",
+        )
+        .hidden(true);
     let verify_index_arg = Arg::with_name("verify_accounts_index")
         .long("verify-accounts-index")
         .takes_value(false)
@@ -1295,6 +1302,7 @@ fn main() {
             .arg(&accounts_filler_count)
             .arg(&accounts_filler_size)
             .arg(&verify_index_arg)
+            .arg(&skip_rewrites_arg)
             .arg(&hard_forks_arg)
             .arg(&no_accounts_db_caching_arg)
             .arg(&accounts_db_test_hash_calculation_arg)
@@ -2096,6 +2104,7 @@ fn main() {
                     index: Some(accounts_index_config),
                     accounts_hash_cache_path: Some(ledger_path.clone()),
                     filler_accounts_config,
+                    skip_rewrites: matches.is_present("accounts_db_skip_rewrites"),
                     ..AccountsDbConfig::default()
                 });
 

runtime/src/accounts_db.rs

@@ -134,6 +134,7 @@ pub const ACCOUNTS_DB_CONFIG_FOR_TESTING: AccountsDbConfig = AccountsDbConfig {
     filler_accounts_config: FillerAccountsConfig::const_default(),
     hash_calc_num_passes: None,
     write_cache_limit_bytes: None,
+    skip_rewrites: false,
 };
 pub const ACCOUNTS_DB_CONFIG_FOR_BENCHMARKS: AccountsDbConfig = AccountsDbConfig {
     index: Some(ACCOUNTS_INDEX_CONFIG_FOR_BENCHMARKS),
@@ -141,6 +142,7 @@ pub const ACCOUNTS_DB_CONFIG_FOR_BENCHMARKS: AccountsDbConfig = AccountsDbConfig
     filler_accounts_config: FillerAccountsConfig::const_default(),
     hash_calc_num_passes: None,
     write_cache_limit_bytes: None,
+    skip_rewrites: false,
 };
 
 pub type BinnedHashData = Vec<Vec<CalculateHashIntermediate>>;
@@ -178,6 +180,7 @@ pub struct AccountsDbConfig {
     pub filler_accounts_config: FillerAccountsConfig,
     pub hash_calc_num_passes: Option<usize>,
     pub write_cache_limit_bytes: Option<u64>,
+    pub skip_rewrites: bool,
 }
 
 struct FoundStoredAccount<'a> {
@@ -1014,6 +1017,9 @@ pub struct AccountsDb {
     /// Keeps tracks of index into AppendVec on a per slot basis
     pub accounts_index: AccountInfoAccountsIndex,
 
+    /// true iff rent exempt accounts are not rewritten in their normal rent collection slot
+    pub skip_rewrites: bool,
+
     pub storage: AccountStorage,
 
     pub accounts_cache: AccountsCache,
@@ -1624,6 +1630,7 @@ impl AccountsDb {
 
         AccountsDb {
             active_stats: ActiveStats::default(),
+            skip_rewrites: false,
             accounts_index,
             storage: AccountStorage::default(),
             accounts_cache: AccountsCache::default(),
@@ -1716,6 +1723,10 @@ impl AccountsDb {
             .as_ref()
             .map(|config| config.filler_accounts_config)
             .unwrap_or_default();
+        let skip_rewrites = accounts_db_config
+            .as_ref()
+            .map(|config| config.skip_rewrites)
+            .unwrap_or_default();
 
         let filler_account_suffix = if filler_accounts_config.count > 0 {
             Some(solana_sdk::pubkey::new_rand())
@@ -1725,6 +1736,7 @@ impl AccountsDb {
         let paths_is_empty = paths.is_empty();
         let mut new = Self {
             paths,
+            skip_rewrites,
             cluster_type: Some(*cluster_type),
             account_indexes,
             caching_enabled,

validator/src/main.rs

@@ -1540,6 +1540,13 @@ pub fn main() {
                 .help("Enables faster starting of validators by skipping shrink. \
                       This option is for use during testing."),
         )
+        .arg(
+            Arg::with_name("accounts_db_skip_rewrites")
+                .long("accounts-db-skip-rewrites")
+                .help("Accounts that are rent exempt and have no changes are not rewritten. \
+                      This produces snapshots that older versions cannot read.")
+                      .hidden(true),
+        )
         .arg(
             Arg::with_name("accounts_db_cache_limit_mb")
                 .long("accounts-db-cache-limit-mb")
@@ -2276,6 +2283,7 @@ pub fn main() {
         write_cache_limit_bytes: value_t!(matches, "accounts_db_cache_limit_mb", u64)
             .ok()
             .map(|mb| mb * MB as u64),
+        skip_rewrites: matches.is_present("accounts_db_skip_rewrites"),
         ..AccountsDbConfig::default()
     };