Sqlite: use repsertMany instead of deleteMany+putMany

The function repsertMany does what I thought putMany did. When there
is a conflict it updates the rows. This means that we don't need to
delete before inserting.

lib/core/src/Cardano/Wallet/DB/Sqlite.hs

@@ -549,22 +549,41 @@ deleteTxMetas
 deleteTxMetas wid = deleteWhere [ TxMetaTableWalletId ==. wid ]
 
 -- | Add new TxMeta rows, overwriting existing ones.
-putTxMetas
-    :: W.WalletId
-    -> [TxMeta]
-    -> SqlPersistM ()
-putTxMetas wid metas = do
-    let txids = map txMetaTableTxId metas
-    deleteMany [ TxMetaTableWalletId ==. wid ] TxMetaTableTxId txids
-    insertMany_ metas
+putTxMetas :: [TxMeta] -> SqlPersistM ()
+putTxMetas metas = dbChunked repsertMany
+    [(TxMetaKey txMetaTableTxId txMetaTableWalletId, m) | m@TxMeta{..} <- metas]
 
 -- | Insert multiple transactions, removing old instances first.
-putTxs :: [TxId] -> [TxIn] -> [TxOut] -> SqlPersistM ()
-putTxs txIds txins txouts = do
-    deleteMany [] TxInputTableTxId txIds
-    putMany txins
-    deleteMany [] TxOutputTableTxId txIds
-    putMany txouts
+putTxs :: [TxIn] -> [TxOut] -> SqlPersistM ()
+putTxs txins txouts = do
+    dbChunked repsertMany
+        [ (TxInKey txInputTableTxId txInputTableSourceTxId txInputTableSourceIndex, i)
+        | i@TxIn{..} <- txins ]
+    dbChunked repsertMany
+        [ (TxOutKey txOutputTableTxId txOutputTableIndex, o)
+        | o@TxOut{..} <- txouts ]
+
+-- | Convert a single DB "updateMany" (or similar) query into multiple
+-- updateMany queries with smaller lists of values.
+--
+-- This is to prevent too many variables appearing in the SQL statement.
+-- SQLITE_MAX_VARIABLE_NUMBER is 999 by default, and we will get a
+-- "too many SQL variables" exception if that is exceeded.
+--
+-- We choose a conservative 100 because there can be multiple variables
+-- per row updated.
+dbChunked :: ([a] -> SqlPersistM b) -> [a] -> SqlPersistM ()
+dbChunked = chunkedM 100
+
+-- | Given an action which takes a list of items, and a list of items, run that
+-- action multiple times with the input list cut into chunks.
+chunkedM
+    :: Monad m
+    => Int -- ^ Chunk size
+    -> ([a] -> m b) -- ^ Action to run on values
+    -> [a] -- ^ The values
+    -> m ()
+chunkedM n f = mapM_ f . chunksOf n
 
 -- | Delete transactions that aren't referred to by either Pending or TxMeta of
 -- any wallet.