reworks blockstore Column trait and LedgerColumn struct (#4416)

Column::serialize_index assumes that the &mut [u8] buffer is of size
Column::KEY_LEN but there is no type-safety to ensure that:
https://github.com/anza-xyz/agave/blob/c33c0392e/ledger/src/blockstore_db.rs#L779

Column::serialize_index also forces a non-idiomatic usage, e.g:
https://github.com/anza-xyz/agave/blob/c33c0392e/ledger/src/blockstore_db.rs#L1624-L1627
https://github.com/anza-xyz/agave/blob/c33c0392e/ledger/src/blockstore_db.rs#L1636-L1639

Separately, Column::key allocates a vector on heap whereas an array
suffices:
https://github.com/anza-xyz/agave/blob/c33c0392e/ledger/src/blockstore_db.rs#L781

LedgerColumn takes a const K: usize type parameter which duplicates what
Column::KEY_LEN is supposed to do:
https://github.com/anza-xyz/agave/blob/c33c0392e/ledger/src/blockstore_db.rs#L1335

This also results in a very verbose LedgerColumn type specification
which repeats Column::KEY_LEN in the type:
https://github.com/anza-xyz/agave/blob/c33c0392e/ledger/src/blockstore.rs#L239-L260

LedgerColumn also duplicates Column::{key,serialize_index} by
implementing key_from_index:
https://github.com/anza-xyz/agave/blob/c33c0392e/ledger/src/blockstore_db.rs#L1427-L1432

This commit removes:

    const KEY_LEN: usize;
    fn serialize_index(key: &mut [u8], index: Self::Index);

from the definition of Column trait and instead adds:

    type Key: AsRef<[u8]>;

This also allows to remove const K: usize type parameter from the
definition of LedgerColumn, remove LedgerColumn::key_from_index and
avoid heap allocation in Collumn::key.

ledger/src/blockstore.rs

@@ -236,28 +236,27 @@ pub struct Blockstore {
     ledger_path: PathBuf,
     db: Arc<Rocks>,
     // Column families
-    address_signatures_cf: LedgerColumn<cf::AddressSignatures, { cf::AddressSignatures::KEY_LEN }>,
-    bank_hash_cf: LedgerColumn<cf::BankHash, { cf::BankHash::KEY_LEN }>,
-    block_height_cf: LedgerColumn<cf::BlockHeight, { cf::BlockHeight::KEY_LEN }>,
-    blocktime_cf: LedgerColumn<cf::Blocktime, { cf::Blocktime::KEY_LEN }>,
-    code_shred_cf: LedgerColumn<cf::ShredCode, { cf::ShredCode::KEY_LEN }>,
-    data_shred_cf: LedgerColumn<cf::ShredData, { cf::ShredData::KEY_LEN }>,
-    dead_slots_cf: LedgerColumn<cf::DeadSlots, { cf::DeadSlots::KEY_LEN }>,
-    duplicate_slots_cf: LedgerColumn<cf::DuplicateSlots, { cf::DuplicateSlots::KEY_LEN }>,
-    erasure_meta_cf: LedgerColumn<cf::ErasureMeta, { cf::ErasureMeta::KEY_LEN }>,
-    index_cf: LedgerColumn<cf::Index, { cf::Index::KEY_LEN }>,
-    merkle_root_meta_cf: LedgerColumn<cf::MerkleRootMeta, { cf::MerkleRootMeta::KEY_LEN }>,
-    meta_cf: LedgerColumn<cf::SlotMeta, { cf::SlotMeta::KEY_LEN }>,
-    optimistic_slots_cf: LedgerColumn<cf::OptimisticSlots, { cf::OptimisticSlots::KEY_LEN }>,
-    orphans_cf: LedgerColumn<cf::Orphans, { cf::Orphans::KEY_LEN }>,
-    perf_samples_cf: LedgerColumn<cf::PerfSamples, { cf::PerfSamples::KEY_LEN }>,
-    program_costs_cf: LedgerColumn<cf::ProgramCosts, { cf::ProgramCosts::KEY_LEN }>,
-    rewards_cf: LedgerColumn<cf::Rewards, { cf::Rewards::KEY_LEN }>,
-    roots_cf: LedgerColumn<cf::Root, { cf::Root::KEY_LEN }>,
-    transaction_memos_cf: LedgerColumn<cf::TransactionMemos, { cf::TransactionMemos::KEY_LEN }>,
-    transaction_status_cf: LedgerColumn<cf::TransactionStatus, { cf::TransactionStatus::KEY_LEN }>,
-    transaction_status_index_cf:
-        LedgerColumn<cf::TransactionStatusIndex, { cf::TransactionStatusIndex::KEY_LEN }>,
+    address_signatures_cf: LedgerColumn<cf::AddressSignatures>,
+    bank_hash_cf: LedgerColumn<cf::BankHash>,
+    block_height_cf: LedgerColumn<cf::BlockHeight>,
+    blocktime_cf: LedgerColumn<cf::Blocktime>,
+    code_shred_cf: LedgerColumn<cf::ShredCode>,
+    data_shred_cf: LedgerColumn<cf::ShredData>,
+    dead_slots_cf: LedgerColumn<cf::DeadSlots>,
+    duplicate_slots_cf: LedgerColumn<cf::DuplicateSlots>,
+    erasure_meta_cf: LedgerColumn<cf::ErasureMeta>,
+    index_cf: LedgerColumn<cf::Index>,
+    merkle_root_meta_cf: LedgerColumn<cf::MerkleRootMeta>,
+    meta_cf: LedgerColumn<cf::SlotMeta>,
+    optimistic_slots_cf: LedgerColumn<cf::OptimisticSlots>,
+    orphans_cf: LedgerColumn<cf::Orphans>,
+    perf_samples_cf: LedgerColumn<cf::PerfSamples>,
+    program_costs_cf: LedgerColumn<cf::ProgramCosts>,
+    rewards_cf: LedgerColumn<cf::Rewards>,
+    roots_cf: LedgerColumn<cf::Root>,
+    transaction_memos_cf: LedgerColumn<cf::TransactionMemos>,
+    transaction_status_cf: LedgerColumn<cf::TransactionStatus>,
+    transaction_status_index_cf: LedgerColumn<cf::TransactionStatusIndex>,
 
     highest_primary_index_slot: RwLock<Option<Slot>>,
     max_root: AtomicU64,
@@ -2507,7 +2506,7 @@ impl Blockstore {
             DEFAULT_TICKS_PER_SECOND * timestamp().saturating_sub(first_timestamp) / 1000;
 
         // Seek to the first shred with index >= start_index
-        db_iterator.seek(C::key((slot, start_index)));
+        db_iterator.seek(C::key(&(slot, start_index)));
 
         // The index of the first missing shred in the slot
         let mut prev_index = start_index;
@@ -3022,7 +3021,7 @@ impl Blockstore {
                 .is_some_and(|highest_slot| highest_slot >= slot)
         {
             self.transaction_memos_cf
-                .get_raw(&cf::TransactionMemos::deprecated_key(signature))
+                .get_raw(cf::TransactionMemos::deprecated_key(signature))
         } else {
             Ok(memos)
         }

ledger/src/blockstore/blockstore_purge.rs

@@ -803,7 +803,12 @@ pub mod tests {
         assert_eq!(status_entry_iterator.next(), None);
     }
 
-    fn get_index_bounds(blockstore: &Blockstore) -> (Box<[u8]>, Box<[u8]>) {
+    fn get_index_bounds(
+        blockstore: &Blockstore,
+    ) -> (
+        <cf::TransactionStatus as Column>::Key,
+        <cf::TransactionStatus as Column>::Key,
+    ) {
         let (first_index, _value) = blockstore
             .transaction_status_cf
             .iterator_cf_raw_key(IteratorMode::Start)