The limit is not pushed to JDBC storage plugin.
The following query:
This issue happens since incorrect row count is calculated for JdbcSort.
Drill enforces to use RelNode.estimateRowCount(mq) for calculating row count for all inheritants of Sort rel node (see DrillRelMdRowCount), but JdbcSort doesn't override this method and uses parent one which returns row count of input. So planner choses DrillLimitRel since it has less row count.