fix(clickhouse): nullable storage_key on canonical_beacon_block_access_list

balance/nonce/code/touched access-list changes carry no storage slot. The
column was a non-nullable FixedString(66) and the route appended nil for
them, which zero-pads to 66 raw NUL bytes rather than NULL: ~48.9M rows on
glamsterdam-devnet-7. Those values are not valid hex, so
startsWith(storage_key, '0x') misses them and they render as garbage in
exports and Grafana.

storage_key is part of the table's ORDER BY, so the type cannot be changed
by ALTER. The fix is applied to the original 006 table definition instead,
with allow_nullable_key = 1 (already used in 001_init) so existing devnet
data can be migrated by a rebuild rather than in place.

The zero hash was rejected as a sentinel because storage_read legitimately
has 2.3M rows at real storage slot 0x000..0, which NULL keeps distinct.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: Savid

deploy/migrations/clickhouse/xatu/006_gloas_bals_support.up.sql

@@ -33,7 +33,10 @@ CREATE TABLE IF NOT EXISTS canonical_beacon_block_access_list_local ON CLUSTER '
     address FixedString(42) CODEC(ZSTD(1)),
     change_type LowCardinality(String) CODEC(ZSTD(1)),
     block_access_index UInt32 CODEC(DoubleDelta, ZSTD(1)),
-    storage_key FixedString(66) CODEC(ZSTD(1)),
+    -- Nullable: balance/nonce/code/touched changes carry no storage slot. A
+    -- non-nullable FixedString would store 66 raw NUL bytes for them, which is
+    -- not valid hex, and the zero hash is ambiguous with real storage slot 0.
+    storage_key Nullable(FixedString(66)) CODEC(ZSTD(1)),
     new_value Nullable(String) CODEC(ZSTD(1)),
     meta_client_name LowCardinality(String) CODEC(ZSTD(1)),
     meta_client_id String CODEC(ZSTD(1)),
@@ -59,7 +62,8 @@ CREATE TABLE IF NOT EXISTS canonical_beacon_block_access_list_local ON CLUSTER '
     meta_labels Map(String, String) CODEC(ZSTD(1))
 ) ENGINE = ReplicatedReplacingMergeTree(updated_date_time)
 PARTITION BY toStartOfMonth(slot_start_date_time)
-ORDER BY (slot_start_date_time, meta_network_name, block_hash, address, change_type, storage_key, block_access_index);
+ORDER BY (slot_start_date_time, meta_network_name, block_hash, address, change_type, storage_key, block_access_index)
+SETTINGS allow_nullable_key = 1;
 
 CREATE TABLE IF NOT EXISTS canonical_beacon_block_access_list ON CLUSTER '{cluster}'
     AS canonical_beacon_block_access_list_local

pkg/clickhouse/route/canonical/canonical_beacon_block_access_list.gen.go

@@ -82,10 +82,12 @@ func (b *canonicalBeaconBlockAccessListBatch) appendPayload(event *xatu.Decorate
 		b.BlockAccessIndex.Append(0)
 	}
 
+	// balance/nonce/code/touched changes carry no storage slot, so store NULL
+	// rather than a zero-padded FixedString of raw NUL bytes.
 	if storageKey := change.GetStorageKey(); storageKey != nil {
-		b.StorageKey.Append([]byte(storageKey.GetValue()))
+		b.StorageKey.Append(proto.NewNullable[[]byte]([]byte(storageKey.GetValue())))
 	} else {
-		b.StorageKey.Append(nil)
+		b.StorageKey.Append(proto.Nullable[[]byte]{})
 	}
 
 	if newValue := change.GetNewValue(); newValue != nil {

pkg/clickhouse/route/canonical/canonical_beacon_block_access_list.go

@@ -81,7 +81,8 @@ func TestSnapshot_canonical_beacon_block_access_list_balance(t *testing.T) {
 		balAddressKey:          "0xaabbccddee112233445566778899aabbccddeeff",
 		balChangeTypeKey:       balChangeTypeBalance,
 		balBlockAccessIndexKey: uint32(2),
-		balStorageKeyKey:       "",
-		balNewValueKey:         "1000000000000000000",
+		// Balance changes carry no storage slot, so storage_key is NULL.
+		balStorageKeyKey: nil,
+		balNewValueKey:   "1000000000000000000",
 	})
 }