Make ephemeral_addresses.address non-null & unique

We should never construct an ephemeral address from an invalid index,
and therefore the address column need not be nullable.

Author: nuttycom

zcash_client_sqlite/src/wallet/db.rs

@@ -116,13 +116,14 @@ pub(super) const TABLE_EPHEMERAL_ADDRESSES: &str = r#"
 CREATE TABLE ephemeral_addresses (
     account_id INTEGER NOT NULL,
     address_index INTEGER NOT NULL,
-    address TEXT,
+    address TEXT NOT NULL,
     used_in_tx INTEGER,
     seen_in_tx INTEGER,
     FOREIGN KEY (account_id) REFERENCES accounts(id),
     FOREIGN KEY (used_in_tx) REFERENCES transactions(id_tx),
     FOREIGN KEY (seen_in_tx) REFERENCES transactions(id_tx),
     PRIMARY KEY (account_id, address_index),
+    CONSTRAINT ephemeral_addr_uniq UNIQUE (address),
     CONSTRAINT used_implies_seen CHECK (
         used_in_tx IS NULL OR seen_in_tx IS NOT NULL
     ),
@@ -135,10 +136,6 @@ CREATE TABLE ephemeral_addresses (
 // libsqlite3-sys requires at least version 3.14.0.
 // "WITHOUT ROWID" tells SQLite to use a clustered index on the (composite) primary key.
 const_assert_eq!(GAP_LIMIT, 20);
-pub(super) const INDEX_EPHEMERAL_ADDRESSES_ADDRESS: &str = r#"
-CREATE INDEX ephemeral_addresses_address ON ephemeral_addresses (
-    address ASC
-)"#;
 
 /// Stores information about every block that the wallet has scanned.
 ///

zcash_client_sqlite/src/wallet/init.rs

@@ -422,7 +422,6 @@ mod tests {
             db::INDEX_ACCOUNTS_UIVK,
             db::INDEX_HD_ACCOUNT,
             db::INDEX_ADDRESSES_ACCOUNTS,
-            db::INDEX_EPHEMERAL_ADDRESSES_ADDRESS,
             db::INDEX_NF_MAP_LOCATOR_IDX,
             db::INDEX_ORCHARD_RECEIVED_NOTES_ACCOUNT,
             db::INDEX_ORCHARD_RECEIVED_NOTES_TX,

zcash_client_sqlite/src/wallet/init/migrations/ephemeral_addresses.rs

@@ -45,24 +45,22 @@ impl<P: consensus::Parameters> RusqliteMigration for Migration<P> {
             "CREATE TABLE ephemeral_addresses (
                 account_id INTEGER NOT NULL,
                 address_index INTEGER NOT NULL,
-                address TEXT,
+                address TEXT NOT NULL,
                 used_in_tx INTEGER,
                 seen_in_tx INTEGER,
                 FOREIGN KEY (account_id) REFERENCES accounts(id),
                 FOREIGN KEY (used_in_tx) REFERENCES transactions(id_tx),
                 FOREIGN KEY (seen_in_tx) REFERENCES transactions(id_tx),
                 PRIMARY KEY (account_id, address_index),
+                CONSTRAINT ephemeral_addr_uniq UNIQUE (address),
                 CONSTRAINT used_implies_seen CHECK (
                     used_in_tx IS NULL OR seen_in_tx IS NOT NULL
                 ),
                 CONSTRAINT index_range_and_address_nullity CHECK (
                     (address_index BETWEEN 0 AND 0x7FFFFFFF AND address IS NOT NULL) OR
                     (address_index BETWEEN 0x80000000 AND 0x7FFFFFFF + 20 AND address IS NULL AND used_in_tx IS NULL AND seen_in_tx IS NULL)
                 )
-            ) WITHOUT ROWID;
-            CREATE INDEX ephemeral_addresses_address ON ephemeral_addresses (
-                address ASC
-            );",
+            ) WITHOUT ROWID;"
         )?;
 
         // Make sure that at least `GAP_LIMIT` ephemeral transparent addresses are

zcash_client_sqlite/src/wallet/transparent/ephemeral.rs

@@ -282,18 +282,19 @@ fn reserve_until<P: consensus::Parameters>(
     )?;
 
     for raw_index in range_to_store {
-        let address_str_opt = match NonHardenedChildIndex::from_index(raw_index) {
-            Some(address_index) => Some(
+        let address_str = NonHardenedChildIndex::from_index(raw_index)
+            .map(|address_index| {
                 ephemeral_ivk
-                    .derive_ephemeral_address(address_index)?
-                    .encode(params),
-            ),
-            None => None,
-        };
+                    .derive_ephemeral_address(address_index)
+                    .map(|addr| addr.encode(params))
+            })
+            .transpose()?
+            .expect("we do not attempt to generate addresses outside the non-hardened index range");
+
         stmt_insert_ephemeral_address.execute(named_params![
             ":account_id": account_id.0,
             ":address_index": raw_index,
-            ":address": address_str_opt,
+            ":address": address_str,
         ])?;
     }
     Ok(())