Sync ForgerCommitment and use it in coord

Previously the coordinator was erroneously using Slot.BatchesLen to determine
when anyone can forge.  The correct behaviour is implmenented with the boolean
flag `ForgerCommitment`, that is set to true only when there's a batch before
the deadline within a slot.

Delete Slot.BatchesLen, and the synchronization code of this value from the
Synchronizer, as this is not needed

db/historydb/historydb.go

@@ -293,11 +293,15 @@ func (hdb *HistoryDB) GetBatches(from, to common.BatchNum) ([]common.Batch, erro
 	return db.SlicePtrsToSlice(batches).([]common.Batch), tracerr.Wrap(err)
 }
 
-// GetBatchesLen retrieve number of batches from the DB, given a slotNum
-func (hdb *HistoryDB) GetBatchesLen(slotNum int64) (int, error) {
-	row := hdb.db.QueryRow("SELECT COUNT(*) FROM batch WHERE slot_num = $1;", slotNum)
-	var batchesLen int
-	return batchesLen, tracerr.Wrap(row.Scan(&batchesLen))
+// GetFirstBatchBlockNumBySlot returns the ethereum block number of the first
+// batch within a slot
+func (hdb *HistoryDB) GetFirstBatchBlockNumBySlot(slotNum int64) (int64, error) {
+	row := hdb.db.QueryRow(
+		`SELECT eth_block_num FROM batch
+		WHERE slot_num = $1 ORDER BY batch_num ASC LIMIT 1;`, slotNum,
+	)
+	var blockNum int64
+	return blockNum, tracerr.Wrap(row.Scan(&blockNum))
 }
 
 // GetLastBatchNum returns the BatchNum of the latest forged batch

db/historydb/historydb_test.go

@@ -1051,6 +1051,70 @@ func TestGetLastTxsPosition(t *testing.T) {
 	assert.Equal(t, sql.ErrNoRows.Error(), err.Error())
 }
 
+func TestGetFirstBatchBlockNumBySlot(t *testing.T) {
+	test.WipeDB(historyDB.DB())
+
+	set := `
+		Type: Blockchain
+
+		// Slot = 0
+
+		> block // 2
+		> block // 3
+		> block // 4
+		> block // 5
+
+		// Slot = 1
+
+		> block // 6
+		> block // 7
+		> batch
+		> block // 8
+		> block // 9
+
+		// Slot = 2
+
+		> batch
+		> block // 10
+		> block // 11
+		> block // 12
+		> block // 13
+
+	`
+	tc := til.NewContext(uint16(0), common.RollupConstMaxL1UserTx)
+	blocks, err := tc.GenerateBlocks(set)
+	assert.NoError(t, err)
+
+	tilCfgExtra := til.ConfigExtra{
+		CoordUser: "A",
+	}
+	err = tc.FillBlocksExtra(blocks, &tilCfgExtra)
+	require.NoError(t, err)
+
+	for i := range blocks {
+		for j := range blocks[i].Rollup.Batches {
+			blocks[i].Rollup.Batches[j].Batch.SlotNum = int64(i) / 4
+		}
+	}
+
+	// Add all blocks
+	for i := range blocks {
+		err = historyDB.AddBlockSCData(&blocks[i])
+		require.NoError(t, err)
+	}
+
+	_, err = historyDB.GetFirstBatchBlockNumBySlot(0)
+	require.Equal(t, sql.ErrNoRows, tracerr.Unwrap(err))
+
+	bn1, err := historyDB.GetFirstBatchBlockNumBySlot(1)
+	require.NoError(t, err)
+	assert.Equal(t, int64(8), bn1)
+
+	bn2, err := historyDB.GetFirstBatchBlockNumBySlot(2)
+	require.NoError(t, err)
+	assert.Equal(t, int64(10), bn2)
+}
+
 // setTestBlocks WARNING: this will delete the blocks and recreate them
 func setTestBlocks(from, to int64) []common.Block {
 	test.WipeDB(historyDB.DB())