Lambda Expression

JEXL Function

Java Expression Language (JEXL) is an expression language engine. We use JEXL to extend UDFs, which are implemented on the command line with simple lambda expressions. See the link for operators supported in jexl lambda expressionsLambda - 图1open in new window.

Function NameAllowed Input Series Data TypesRequired AttributesOutput Series Data TypeSeries Data Type Description
JEXLINT32 / INT64 / FLOAT / DOUBLE / TEXT / BOOLEANexpr is a lambda expression that supports standard one or multi arguments in the form x -> {…} or (x, y, z) -> {…}, e.g. x -> {x 2}, (x, y, z) -> {x + y z}INT32 / INT64 / FLOAT / DOUBLE / TEXT / BOOLEANReturns the input time series transformed by a lambda expression

Demonstrate

Example data: root.ln.wf01.wt01.temperature, root.ln.wf01.wt01.st, root.ln.wf01.wt01.str a total of 11 data.

  1. IoTDB> select * from root.ln.wf01.wt01;
  2. +-----------------------------+---------------------+--------------------+-----------------------------+
  3. |                         Time|root.ln.wf01.wt01.str|root.ln.wf01.wt01.st|root.ln.wf01.wt01.temperature|
  4. +-----------------------------+---------------------+--------------------+-----------------------------+
  5. |1970-01-01T08:00:00.000+08:00|                  str|                10.0|                          0.0|
  6. |1970-01-01T08:00:00.001+08:00|                  str|                20.0|                          1.0|
  7. |1970-01-01T08:00:00.002+08:00|                  str|                30.0|                          2.0|
  8. |1970-01-01T08:00:00.003+08:00|                  str|                40.0|                          3.0|
  9. |1970-01-01T08:00:00.004+08:00|                  str|                50.0|                          4.0|
  10. |1970-01-01T08:00:00.005+08:00|                  str|                60.0|                          5.0|
  11. |1970-01-01T08:00:00.006+08:00|                  str|                70.0|                          6.0|
  12. |1970-01-01T08:00:00.007+08:00|                  str|                80.0|                          7.0|
  13. |1970-01-01T08:00:00.008+08:00|                  str|                90.0|                          8.0|
  14. |1970-01-01T08:00:00.009+08:00|                  str|               100.0|                          9.0|
  15. |1970-01-01T08:00:00.010+08:00|                  str|               110.0|                         10.0|
  16. +-----------------------------+---------------------+--------------------+-----------------------------+

Sql:

  1. select jexl(temperature, 'expr'='x -> {x + x}') as jexl1, jexl(temperature, 'expr'='x -> {x * 3}') as jexl2, jexl(temperature, 'expr'='x -> {x * x}') as jexl3, jexl(temperature, 'expr'='x -> {multiply(x, 100)}') as jexl4, jexl(temperature, st, 'expr'='(x, y) -> {x + y}') as jexl5, jexl(temperature, st, str, 'expr'='(x, y, z) -> {x + y + z}') as jexl6 from root.ln.wf01.wt01;
  2. Result:

+——————————————-+——-+——-+——-+———+——-+————+ | Time|jexl1|jexl2|jexl3| jexl4|jexl5| jexl6| +——————————————-+——-+——-+——-+———+——-+————+ |1970-01-01T08:00:00.000+08:00| 0.0| 0.0| 0.0| 0.0| 10.0| 10.0str| |1970-01-01T08:00:00.001+08:00| 2.0| 3.0| 1.0| 100.0| 21.0| 21.0str| |1970-01-01T08:00:00.002+08:00| 4.0| 6.0| 4.0| 200.0| 32.0| 32.0str| |1970-01-01T08:00:00.003+08:00| 6.0| 9.0| 9.0| 300.0| 43.0| 43.0str| |1970-01-01T08:00:00.004+08:00| 8.0| 12.0| 16.0| 400.0| 54.0| 54.0str| |1970-01-01T08:00:00.005+08:00| 10.0| 15.0| 25.0| 500.0| 65.0| 65.0str| |1970-01-01T08:00:00.006+08:00| 12.0| 18.0| 36.0| 600.0| 76.0| 76.0str| |1970-01-01T08:00:00.007+08:00| 14.0| 21.0| 49.0| 700.0| 87.0| 87.0str| |1970-01-01T08:00:00.008+08:00| 16.0| 24.0| 64.0| 800.0| 98.0| 98.0str| |1970-01-01T08:00:00.009+08:00| 18.0| 27.0| 81.0| 900.0|109.0|109.0str| |1970-01-01T08:00:00.010+08:00| 20.0| 30.0|100.0|1000.0|120.0|120.0str| +——————————————-+——-+——-+——-+———+——-+————+ Total line number = 11 It costs 0.118s ```