Merge bitcoin/bitcoin#27790: walletdb: Add PrefixCursor

ba616b932cb9e9adb7eb9f1826caa62ce422a22d wallet: Add GetPrefixCursor to DatabaseBatch (Andrew Chow)
1d858b055daeea363e0450f327672658548be4c6 walletdb: Handle when database keys are empty (Ryan Ofsky)
84b2f353bbefb9264284e7430863b2fa1d796d38 walletdb: Consistently clear key and value streams before writing (Andrew Chow)

Pull request description:

  Split from #24914 as suggested in https://github.com/bitcoin/bitcoin/pull/24914#pullrequestreview-1442091917

  This PR adds a wallet database cursor that gives a view over all of the records beginning with the same prefix.

ACKs for top commit:
  ryanofsky:
    Code review ACK ba616b932cb9e9adb7eb9f1826caa62ce422a22d. Just suggested changes since last review
  furszy:
    ACK ba616b93

Tree-SHA512: 38a61849f108d8003d28c599b1ad0421ac9beb3afe14c02f1253e7b4efc3d4eef483e32647a820fc6636bca3f9efeff9fe062b6b602e0cded69f21f8b26af544

1 files changed, 10 insertions, 0 deletions

diff --git a/src/wallet/sqlite.h b/src/wallet/sqlite.h
index d9de40569b..0378bbb8d6 100644
--- a/src/wallet/sqlite.h
+++ b/src/wallet/sqlite.h
@@ -15,12 +15,21 @@ struct bilingual_str;
 namespace wallet {
 class SQLiteDatabase;
 
+/** RAII class that provides a database cursor */
 class SQLiteCursor : public DatabaseCursor
 {
 public:
     sqlite3_stmt* m_cursor_stmt{nullptr};
+    // Copies of the prefix things for the prefix cursor.
+    // Prevents SQLite from accessing temp variables for the prefix things.
+    std::vector<std::byte> m_prefix_range_start;
+    std::vector<std::byte> m_prefix_range_end;
 
     explicit SQLiteCursor() {}
+    explicit SQLiteCursor(std::vector<std::byte> start_range, std::vector<std::byte> end_range)
+        : m_prefix_range_start(std::move(start_range)),
+        m_prefix_range_end(std::move(end_range))
+    {}
     ~SQLiteCursor() override;
 
     Status Next(DataStream& key, DataStream& value) override;
@@ -57,6 +66,7 @@ public:
     void Close() override;
 
     std::unique_ptr<DatabaseCursor> GetNewCursor() override;
+    std::unique_ptr<DatabaseCursor> GetNewPrefixCursor(Span<const std::byte> prefix) override;
     bool TxnBegin() override;
     bool TxnCommit() override;
     bool TxnAbort() override;