feat: added Tail function

CHANGELOG.md

@@ -1,5 +1,8 @@
 ## 1.15.0 [unreleased]
 
+### Features
+1. [#191](https://github.com/influxdata/influxdb-client-java/pull/191): Added tail operator to FluxDSL
+
 ## 1.14.0 [2020-12-04]
 
 ### Features

flux-dsl/README.md

@@ -663,6 +663,22 @@ Flux flux = Flux
  .from("telegraf")
  .sum();
 ```
+
+### tail
+Tail caps the number of records in output tables to a fixed size [[doc](http://bit.ly/flux-spec#tail)].
+- `n` - The maximum number of records to output. [int]
+- `offset` - The number of records to skip per table. Default to `0`. [int]
+```java
+Flux flux = Flux
+ .from("telegraf")
+ .tail(5);
+``` 
+```java
+Flux flux = Flux
+ .from("telegraf")
+ .tail(100, 10);
+```
+
 ### to
 The To operation takes data from a stream and writes it to a bucket [[doc](http://bit.ly/flux-spec#to)].
 - `bucket` - The bucket to which data will be written. [string]

flux-dsl/src/main/java/com/influxdb/query/dsl/Flux.java

@@ -67,6 +67,7 @@
 import com.influxdb.query.dsl.functions.SpreadFlux;
 import com.influxdb.query.dsl.functions.StddevFlux;
 import com.influxdb.query.dsl.functions.SumFlux;
+import com.influxdb.query.dsl.functions.TailFlux;
 import com.influxdb.query.dsl.functions.ToBoolFlux;
 import com.influxdb.query.dsl.functions.ToDurationFlux;
 import com.influxdb.query.dsl.functions.ToFloatFlux;
@@ -1717,6 +1718,50 @@ public final SumFlux sum(@Nonnull final String column) {
  return new SumFlux(this).withColumn(column);
  }
 
+ /**
+ * Caps the number of records in output tables.
+ *
+ * <h3>The parameters had to be defined by:</h3>
+ * <ul>
+ * <li>{@link TailFlux#withN(int)}</li>
+ * <li>{@link TailFlux#withPropertyNamed(String)}</li>
+ * <li>{@link TailFlux#withPropertyNamed(String, String)}</li>
+ * <li>{@link TailFlux#withPropertyValueEscaped(String, String)}</li>
+ * </ul>
+ *
+ * @return {@link TailFlux}
+ */
+ @Nonnull
+ public final TailFlux tail() {
+
+ return new TailFlux(this);
+ }
+
+ /**
+ * Caps the number of records in output tables.
+ *
+ * @param numberOfResults The number of results
+ * @return {@link TailFlux}
+ */
+ @Nonnull
+ public final TailFlux tail(final int numberOfResults) {
+
+ return new TailFlux(this).withN(numberOfResults);
+ }
+
+ /**
+ * Caps the number of records in output tables.
+ *
+ * @param numberOfResults The number of results
+ * @param offset The number of records to skip per table.
+ * @return {@link TailFlux}
+ */
+ @Nonnull
+ public final TailFlux tail(final int numberOfResults, final int offset) {
+
+ return new TailFlux(this).withN(numberOfResults).withOffset(offset);
+ }
+
  /**
  * To operation takes data from a stream and writes it to a bucket.
  *

flux-dsl/src/main/java/com/influxdb/query/dsl/functions/TailFlux.java

@@ -0,0 +1,86 @@
+/*
+ * The MIT License
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.influxdb.query.dsl.functions;
+
+import javax.annotation.Nonnull;
+
+import com.influxdb.Arguments;
+import com.influxdb.query.dsl.Flux;
+
+/**
+ * Tail caps the number of records in output tables to a fixed size <i>n</i>.
+ * <a href="http://bit.ly/flux-spec#tail">See SPEC</a>.
+ *
+ * <h3>Options</h3>
+ * <ul>
+ * <li><b>n</b> - The maximum number of records to output [int].</li>
+ * <li><b>offset</b> - The number of records to skip per table [int]. Default to <i>0</i>.</li>
+ * </ul>
+ *
+ * <h3>Example</h3>
+ * <pre>
+ * Flux flux = Flux
+ * .from("telegraf")
+ * .tail(5);
+ * </pre>
+ *
+ * @author Jakub Bednar (14/12/2020 10:20)
+ */
+public final class TailFlux extends AbstractParametrizedFlux {
+ public TailFlux(@Nonnull final Flux flux) {
+ super(flux);
+ }
+
+ @Nonnull
+ @Override
+ protected String operatorName() {
+ return "tail";
+ }
+
+ /**
+ * @param numberOfResults The number of results
+ * @return this
+ */
+ @Nonnull
+ public TailFlux withN(final int numberOfResults) {
+
+ Arguments.checkPositiveNumber(numberOfResults, "Number of results");
+
+ this.withPropertyValue("n", numberOfResults);
+
+ return this;
+ }
+
+ /**
+ * @param offset The number of records to skip per table.
+ * @return this
+ */
+ @Nonnull
+ public TailFlux withOffset(final int offset) {
+
+ Arguments.checkNotNegativeNumber(offset, "The number of records to skip");
+
+ this.withPropertyValue("offset", offset);
+
+ return this;
+ }
+}

flux-dsl/src/test/java/com/influxdb/query/dsl/functions/TailFluxTest.java

@@ -0,0 +1,100 @@
+/*
+ * The MIT License
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.influxdb.query.dsl.functions;
+
+import java.util.HashMap;
+
+import com.influxdb.query.dsl.Flux;
+
+import org.assertj.core.api.Assertions;
+import org.junit.jupiter.api.Test;
+import org.junit.platform.runner.JUnitPlatform;
+import org.junit.runner.RunWith;
+
+/**
+ * @author Jakub Bednar (14/12/2020 10:24)
+ */
+@RunWith(JUnitPlatform.class)
+class TailFluxTest
+{
+@Test
+void tail() {
+
+Flux flux = Flux
+.from("telegraf")
+.tail(5);
+
+Assertions.assertThat(flux.toString()).isEqualToIgnoringWhitespace("from(bucket:\"telegraf\") |> tail(n: 5)");
+}
+
+@Test
+void tailOffset() {
+
+Flux flux = Flux
+.from("telegraf")
+.tail(100, 10);
+
+Assertions.assertThat(flux.toString())
+.isEqualToIgnoringWhitespace("from(bucket:\"telegraf\") |> tail(n: 100, offset:10)");
+}
+
+@Test
+void tailOffsetZero() {
+
+Flux flux = Flux
+.from("telegraf")
+.tail(100, 0);
+
+Assertions.assertThat(flux.toString())
+.isEqualToIgnoringWhitespace("from(bucket:\"telegraf\") |> tail(n: 100, offset:0)");
+}
+
+@Test
+void tailPositive() {
+Assertions.assertThatThrownBy(() -> Flux.from("telegraf").tail(-5))
+.isInstanceOf(IllegalArgumentException.class)
+.hasMessage("Expecting a positive number for Number of results");
+}
+
+@Test
+void tailByParameter() {
+
+Flux flux = Flux
+.from("telegraf")
+.tail()
+.withPropertyNamed("n", "tail");
+
+HashMap<String, Object> parameters = new HashMap<>();
+parameters.put("tail", 15);
+
+Assertions.assertThat(flux.toString(parameters))
+.isEqualToIgnoringWhitespace("from(bucket:\"telegraf\") |> tail(n: 15)");
+}
+
+@Test
+void tailByParameterMissing() {
+
+Assertions.assertThatThrownBy(() -> Flux.from("telegraf").tail().withPropertyNamed("tail").toString())
+.isInstanceOf(IllegalStateException.class)
+.hasMessage("The parameter 'tail' is not defined.");
+}
+}