From fbc212d85880b11d5f0c3f634970d202fb2fbd67 Mon Sep 17 00:00:00 2001
From: Jihoon Son <jihoonson@apache.org>
Date: Thu, 13 Aug 2015 12:05:32 +0900
Subject: [PATCH 1/3] TAJO-1754

---
 .../function/json/JsonArrayContains.java      | 103 ++++++++++++++++++
 .../engine/function/json/JsonArrayGet.java    |  82 ++++++++++++++
 .../engine/function/json/JsonArrayLength.java |  67 ++++++++++++
 .../function/json/JsonExtractPathText.java    |  12 +-
 .../function/json/ScalarJsonFunction.java     |  20 ++++
 .../engine/function/TestJsonFunctions.java    |  31 ++++++
 6 files changed, 307 insertions(+), 8 deletions(-)
 create mode 100644 tajo-core/src/main/java/org/apache/tajo/engine/function/json/JsonArrayContains.java
 create mode 100644 tajo-core/src/main/java/org/apache/tajo/engine/function/json/JsonArrayGet.java
 create mode 100644 tajo-core/src/main/java/org/apache/tajo/engine/function/json/JsonArrayLength.java
 create mode 100644 tajo-core/src/main/java/org/apache/tajo/engine/function/json/ScalarJsonFunction.java

diff --git a/tajo-core/src/main/java/org/apache/tajo/engine/function/json/JsonArrayContains.java b/tajo-core/src/main/java/org/apache/tajo/engine/function/json/JsonArrayContains.java
new file mode 100644
index 0000000000..c0287a9336
--- /dev/null
+++ b/tajo-core/src/main/java/org/apache/tajo/engine/function/json/JsonArrayContains.java
@@ -0,0 +1,103 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.tajo.engine.function.json;
+
+import net.minidev.json.JSONArray;
+import net.minidev.json.parser.ParseException;
+import org.apache.tajo.catalog.Column;
+import org.apache.tajo.common.TajoDataTypes;
+import org.apache.tajo.common.TajoDataTypes.Type;
+import org.apache.tajo.datum.AnyDatum;
+import org.apache.tajo.datum.BooleanDatum;
+import org.apache.tajo.datum.Datum;
+import org.apache.tajo.datum.NullDatum;
+import org.apache.tajo.engine.function.annotation.Description;
+import org.apache.tajo.engine.function.annotation.ParamTypes;
+import org.apache.tajo.storage.Tuple;
+
+@Description(
+    functionName = "json_array_contains",
+    description = "Determine if the given value exists in the JSON array",
+    detail = "Determine if the given value exists in the JSON array.",
+    example = "> SELECT json_array_contains('[100, 200, 300]', 100);\n" +
+        "t",
+    returnType = Type.BOOLEAN,
+    paramTypes = {@ParamTypes(paramTypes = {Type.TEXT, Type.ANY})}
+)
+public class JsonArrayContains extends ScalarJsonFunction {
+  private boolean isLong;
+  private boolean isDouble;
+  private boolean isFirst = true;
+
+  public JsonArrayContains() {
+    super(new Column[]{
+        new Column("json_array", TajoDataTypes.Type.TEXT),
+        new Column("index", TajoDataTypes.Type.ANY)
+    });
+  }
+
+  @Override
+  public Datum eval(Tuple params) {
+    if (params.isBlankOrNull(0) || params.isBlankOrNull(1)) {
+      return NullDatum.get();
+    }
+
+    try {
+      Object parsed = parser.parse(params.getBytes(0));
+      if (parsed instanceof JSONArray) {
+        JSONArray array = (JSONArray) parsed;
+        Datum actualParam = ((AnyDatum)params.asDatum(1)).getActual();
+
+        if (isFirst) {
+          isFirst = false;
+          if (actualParam.type() == TajoDataTypes.Type.INT1 ||
+              actualParam.type() == TajoDataTypes.Type.INT2 ||
+              actualParam.type() == TajoDataTypes.Type.INT4 ||
+              actualParam.type() == TajoDataTypes.Type.INT8) {
+            isLong = true;
+          } else if (actualParam.type() == TajoDataTypes.Type.FLOAT4 ||
+              actualParam.type() == TajoDataTypes.Type.FLOAT8) {
+            isDouble = true;
+          }
+        }
+
+        for (Object eachElem : array) {
+          if (isLong && eachElem instanceof Long) {
+            if (actualParam.asInt8() == (Long)eachElem) {
+              return BooleanDatum.TRUE;
+            }
+          } else if (isDouble && eachElem instanceof Double) {
+            if (actualParam.asFloat8() == (Double)eachElem) {
+              return BooleanDatum.TRUE;
+            }
+          } else {
+            if (actualParam.asChars().equals(eachElem.toString())) {
+              return BooleanDatum.TRUE;
+            }
+          }
+        }
+        return BooleanDatum.FALSE;
+      } else {
+        return NullDatum.get();
+      }
+    } catch (ParseException e) {
+      return NullDatum.get();
+    }
+  }
+}
diff --git a/tajo-core/src/main/java/org/apache/tajo/engine/function/json/JsonArrayGet.java b/tajo-core/src/main/java/org/apache/tajo/engine/function/json/JsonArrayGet.java
new file mode 100644
index 0000000000..d27a134662
--- /dev/null
+++ b/tajo-core/src/main/java/org/apache/tajo/engine/function/json/JsonArrayGet.java
@@ -0,0 +1,82 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.tajo.engine.function.json;
+
+import net.minidev.json.JSONArray;
+import net.minidev.json.parser.ParseException;
+import org.apache.tajo.catalog.Column;
+import org.apache.tajo.common.TajoDataTypes;
+import org.apache.tajo.datum.Datum;
+import org.apache.tajo.datum.DatumFactory;
+import org.apache.tajo.datum.NullDatum;
+import org.apache.tajo.engine.function.annotation.Description;
+import org.apache.tajo.engine.function.annotation.ParamTypes;
+import org.apache.tajo.storage.Tuple;
+
+@Description(
+    functionName = "json_array_get",
+    description = "Returns the element at the specified index into the JSON array",
+    detail = "Returns the element at the specified index into the JSON array.\n " +
+        "This function returns an element indexed from the end of an array with a negative index,\n " +
+        "and null if the element at the specified index doesn’t exist.",
+    example = "> SELECT json_array_get('[100, 200, 300]', 1);\n" +
+        "100",
+    returnType = TajoDataTypes.Type.TEXT,
+    paramTypes = {@ParamTypes(paramTypes = {TajoDataTypes.Type.TEXT, TajoDataTypes.Type.INT4})}
+)
+public class JsonArrayGet extends ScalarJsonFunction {
+  private int realIndex = Integer.MAX_VALUE;
+
+  public JsonArrayGet() {
+    super(new Column[]{
+        new Column("json_array", TajoDataTypes.Type.TEXT),
+        new Column("index", TajoDataTypes.Type.INT4)
+    });
+  }
+
+  @Override
+  public Datum eval(Tuple params) {
+    if (params.isBlankOrNull(0) || params.isBlankOrNull(1)) {
+      return NullDatum.get();
+    }
+
+    try {
+      Object parsed = parser.parse(params.getBytes(0));
+      if (parsed instanceof JSONArray) {
+        JSONArray array = (JSONArray) parsed;
+        if (realIndex == Integer.MAX_VALUE) {
+          int givenIndex = params.getInt4(1);
+          // Zero and positive given index points out the element from the left side,
+          // while negative given index points out the element from the right side.
+          realIndex = givenIndex < 0 ? array.size() + givenIndex : givenIndex;
+        }
+
+        if (realIndex >= array.size() || realIndex < 0) {
+          return NullDatum.get();
+        } else {
+          return DatumFactory.createText(array.get(realIndex).toString());
+        }
+      } else {
+        return NullDatum.get();
+      }
+    } catch (ParseException e) {
+      return NullDatum.get();
+    }
+  }
+}
diff --git a/tajo-core/src/main/java/org/apache/tajo/engine/function/json/JsonArrayLength.java b/tajo-core/src/main/java/org/apache/tajo/engine/function/json/JsonArrayLength.java
new file mode 100644
index 0000000000..ff0a05a500
--- /dev/null
+++ b/tajo-core/src/main/java/org/apache/tajo/engine/function/json/JsonArrayLength.java
@@ -0,0 +1,67 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.tajo.engine.function.json;
+
+import net.minidev.json.JSONArray;
+import net.minidev.json.parser.ParseException;
+import org.apache.tajo.catalog.Column;
+import org.apache.tajo.common.TajoDataTypes;
+import org.apache.tajo.common.TajoDataTypes.Type;
+import org.apache.tajo.datum.Datum;
+import org.apache.tajo.datum.DatumFactory;
+import org.apache.tajo.datum.NullDatum;
+import org.apache.tajo.engine.function.annotation.Description;
+import org.apache.tajo.engine.function.annotation.ParamTypes;
+import org.apache.tajo.storage.Tuple;
+
+@Description(
+    functionName = "json_array_length",
+    description = "Returns the length of json array",
+    detail = "Returns the length of json array.",
+    example = "> SELECT json_array_length('[100, 200, 300]');\n" +
+        "3",
+    returnType = Type.INT8,
+    paramTypes = {@ParamTypes(paramTypes = {Type.TEXT})}
+)
+public class JsonArrayLength extends ScalarJsonFunction {
+
+  public JsonArrayLength() {
+    super(new Column[]{
+        new Column("string", TajoDataTypes.Type.TEXT),
+    });
+  }
+
+  @Override
+  public Datum eval(Tuple params) {
+    if (params.isBlankOrNull(0)) {
+      return NullDatum.get();
+    }
+    try {
+      Object parsed = parser.parse(params.getBytes(0));
+      if (parsed instanceof JSONArray) {
+        JSONArray array = (JSONArray) parsed;
+        return DatumFactory.createInt8(array.size());
+      } else {
+        return NullDatum.get();
+      }
+    } catch (ParseException e) {
+      return NullDatum.get();
+    }
+  }
+}
diff --git a/tajo-core/src/main/java/org/apache/tajo/engine/function/json/JsonExtractPathText.java b/tajo-core/src/main/java/org/apache/tajo/engine/function/json/JsonExtractPathText.java
index 84c14c6d97..ced77890e5 100644
--- a/tajo-core/src/main/java/org/apache/tajo/engine/function/json/JsonExtractPathText.java
+++ b/tajo-core/src/main/java/org/apache/tajo/engine/function/json/JsonExtractPathText.java
@@ -20,7 +20,6 @@
 
 import com.jayway.jsonpath.JsonPath;
 import net.minidev.json.JSONObject;
-import net.minidev.json.parser.JSONParser;
 import org.apache.tajo.catalog.Column;
 import org.apache.tajo.common.TajoDataTypes;
 import org.apache.tajo.datum.Datum;
@@ -28,13 +27,12 @@
 import org.apache.tajo.datum.NullDatum;
 import org.apache.tajo.engine.function.annotation.Description;
 import org.apache.tajo.engine.function.annotation.ParamTypes;
-import org.apache.tajo.plan.function.GeneralFunction;
 import org.apache.tajo.storage.Tuple;
 
 /**
  * json_extract_path_text(string, string) -
  * Extracts JSON string from a JSON string based on json path specified,
- * and returns JSON string pointed to by xPath.
+ * and returns JSON string pointed to by JSONPath.
  *
  *
  * Returns null if either argument is null.
@@ -45,16 +43,15 @@
  */
 @Description(
     functionName = "json_extract_path_text",
-    description = "Returns JSON string pointed to by xPath",
+    description = "Returns JSON string pointed to by JSONPath",
     detail = "Extracts JSON string from a JSON string based on json path specified,\n"
-        + "and returns JSON string pointed to by xPath.",
+        + "and returns JSON string pointed to by JSONPath.",
     example = "> SELECT json_extract_path_text('{\"sample\" : {\"name\" : \"tajo\"}}','$.sample.name');\n"
         + "tajo",
     returnType = TajoDataTypes.Type.TEXT,
     paramTypes = {@ParamTypes(paramTypes = {TajoDataTypes.Type.TEXT, TajoDataTypes.Type.TEXT})}
 )
-public class JsonExtractPathText extends GeneralFunction {
-  private JSONParser parser;
+public class JsonExtractPathText extends ScalarJsonFunction {
   private JsonPath jsonPath;
 
   public JsonExtractPathText() {
@@ -62,7 +59,6 @@ public JsonExtractPathText() {
         new Column("string", TajoDataTypes.Type.TEXT),
         new Column("string", TajoDataTypes.Type.TEXT),
     });
-    parser = new JSONParser(JSONParser.MODE_JSON_SIMPLE | JSONParser.IGNORE_CONTROL_CHAR);
   }
 
   @Override
diff --git a/tajo-core/src/main/java/org/apache/tajo/engine/function/json/ScalarJsonFunction.java b/tajo-core/src/main/java/org/apache/tajo/engine/function/json/ScalarJsonFunction.java
new file mode 100644
index 0000000000..5a6afe2b29
--- /dev/null
+++ b/tajo-core/src/main/java/org/apache/tajo/engine/function/json/ScalarJsonFunction.java
@@ -0,0 +1,20 @@
+package org.apache.tajo.engine.function.json;
+
+import net.minidev.json.parser.JSONParser;
+import org.apache.tajo.OverridableConf;
+import org.apache.tajo.catalog.Column;
+import org.apache.tajo.plan.expr.FunctionEval;
+import org.apache.tajo.plan.function.GeneralFunction;
+
+public abstract class ScalarJsonFunction extends GeneralFunction {
+  protected JSONParser parser;
+
+  public ScalarJsonFunction(Column[] definedArgs) {
+    super(definedArgs);
+  }
+
+  @Override
+  public void init(OverridableConf queryContext, FunctionEval.ParamType [] paramTypes) {
+    parser = new JSONParser(JSONParser.MODE_JSON_SIMPLE | JSONParser.IGNORE_CONTROL_CHAR);
+  }
+}
diff --git a/tajo-core/src/test/java/org/apache/tajo/engine/function/TestJsonFunctions.java b/tajo-core/src/test/java/org/apache/tajo/engine/function/TestJsonFunctions.java
index 57248a8d45..1792075278 100644
--- a/tajo-core/src/test/java/org/apache/tajo/engine/function/TestJsonFunctions.java
+++ b/tajo-core/src/test/java/org/apache/tajo/engine/function/TestJsonFunctions.java
@@ -25,11 +25,42 @@
 
 public class TestJsonFunctions extends ExprTestBase {
   static final String JSON_DOCUMENT = "{\"map\" : {\"name\" : \"tajo\"}, \"array\" : [1,2,3]}";
+  static final String JSON_ARRAY = "[100,200,300,400,500]";
+  static final String JSON_COMPLEX_ARRAY = "[100, \"test\", \"2015-08-13 11:58:59\", 0.899999999999]";
+  static final String JSON_EMPTY_ARRAY = "[]";
 
   @Test
   public void testJsonExtractPathText() throws TajoException {
     testSimpleEval("select json_extract_path_text('" + JSON_DOCUMENT + "', '$.map.name') ", new String[]{"tajo"});
     testSimpleEval("select json_extract_path_text('" + JSON_DOCUMENT + "', '$.array[1]') ", new String[]{"2"});
+  }
+
+  @Test
+  public void testJsonArrayGet() throws TajoException {
+    testSimpleEval("select json_array_get('" + JSON_ARRAY + "', 0)", new String[]{"100"});
+    testSimpleEval("select json_array_get('" + JSON_ARRAY + "', 2)", new String[]{"300"});
+    testSimpleEval("select json_array_get('" + JSON_ARRAY + "', -1)", new String[]{"500"});
+    testSimpleEval("select json_array_get('" + JSON_ARRAY + "', -2)", new String[]{"400"});
+    testSimpleEval("select json_array_get('" + JSON_ARRAY + "', 10)", new String[]{""});
+    testSimpleEval("select json_array_get('" + JSON_ARRAY + "', -10)", new String[]{""});
+    testSimpleEval("select json_array_get('" + JSON_EMPTY_ARRAY + "', 0)", new String[]{""});
+  }
 
+  @Test
+  public void testJsonArrayContains() throws TajoException {
+    testSimpleEval("select json_array_contains('" + JSON_COMPLEX_ARRAY + "', 100)", new String[]{"t"});
+    testSimpleEval("select json_array_contains('" + JSON_COMPLEX_ARRAY + "', 'test')", new String[]{"t"});
+    testSimpleEval("select json_array_contains('" + JSON_COMPLEX_ARRAY + "', '2015-08-13 11:58:59'::timestamp)",
+        new String[]{"t"});
+    testSimpleEval("select json_array_contains('" + JSON_COMPLEX_ARRAY + "', '2015-08-13 11:58:59'::date)",
+        new String[]{"f"});
+    testSimpleEval("select json_array_contains('" + JSON_COMPLEX_ARRAY + "', 1000)", new String[]{"f"});
+    testSimpleEval("select json_array_contains('" + JSON_COMPLEX_ARRAY + "', 0.899999999999)", new String[]{"t"});
+  }
+
+  @Test
+  public void testJsonArrayLength() throws TajoException {
+    testSimpleEval("select json_array_length('" + JSON_ARRAY + "')", new String[]{"5"});
+    testSimpleEval("select json_array_length('" + JSON_EMPTY_ARRAY + "')", new String[]{"0"});
   }
 }

From 7382d4425403bca3f3151ffafbbe99024ea84c2e Mon Sep 17 00:00:00 2001
From: Jihoon Son <jihoonson@apache.org>
Date: Thu, 13 Aug 2015 12:21:05 +0900
Subject: [PATCH 2/3] add missing license

---
 .../function/json/ScalarJsonFunction.java      | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/tajo-core/src/main/java/org/apache/tajo/engine/function/json/ScalarJsonFunction.java b/tajo-core/src/main/java/org/apache/tajo/engine/function/json/ScalarJsonFunction.java
index 5a6afe2b29..db95aaa988 100644
--- a/tajo-core/src/main/java/org/apache/tajo/engine/function/json/ScalarJsonFunction.java
+++ b/tajo-core/src/main/java/org/apache/tajo/engine/function/json/ScalarJsonFunction.java
@@ -1,3 +1,21 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
 package org.apache.tajo.engine.function.json;
 
 import net.minidev.json.parser.JSONParser;

From a568fef42688fc6fff591bf52af13038f00e99ce Mon Sep 17 00:00:00 2001
From: Jihoon Son <jihoonson@apache.org>
Date: Thu, 13 Aug 2015 12:53:59 +0900
Subject: [PATCH 3/3] Add a document

---
 .../engine/function/json/JsonArrayGet.java    |  2 +-
 .../src/main/sphinx/functions/json_func.rst   | 55 +++++++++++++++++--
 2 files changed, 51 insertions(+), 6 deletions(-)

diff --git a/tajo-core/src/main/java/org/apache/tajo/engine/function/json/JsonArrayGet.java b/tajo-core/src/main/java/org/apache/tajo/engine/function/json/JsonArrayGet.java
index d27a134662..412337ec02 100644
--- a/tajo-core/src/main/java/org/apache/tajo/engine/function/json/JsonArrayGet.java
+++ b/tajo-core/src/main/java/org/apache/tajo/engine/function/json/JsonArrayGet.java
@@ -36,7 +36,7 @@
         "This function returns an element indexed from the end of an array with a negative index,\n " +
         "and null if the element at the specified index doesn’t exist.",
     example = "> SELECT json_array_get('[100, 200, 300]', 1);\n" +
-        "100",
+        "200",
     returnType = TajoDataTypes.Type.TEXT,
     paramTypes = {@ParamTypes(paramTypes = {TajoDataTypes.Type.TEXT, TajoDataTypes.Type.INT4})}
 )
diff --git a/tajo-docs/src/main/sphinx/functions/json_func.rst b/tajo-docs/src/main/sphinx/functions/json_func.rst
index d05cc1baa4..904be5b587 100644
--- a/tajo-docs/src/main/sphinx/functions/json_func.rst
+++ b/tajo-docs/src/main/sphinx/functions/json_func.rst
@@ -2,16 +2,61 @@
 JSON Functions
 *******************************
 
-.. function:: json_extract_path_text (string json, string xpath)
+.. function:: json_extract_path_text (string json, string json_path)
 
-  Extracts JSON string from a JSON string based on json path specified and returns JSON string pointed to by xPath
+  Extracts JSON string from a JSON string based on json path specified and returns JSON string pointed to by JSONPath.
+  Returns null if either argument is null.
 
-  :param string:
-  :param string:
+  :param json: JSON string
+  :param json_path: JSONpath
   :rtype: text
   :example:
 
   .. code-block:: sql
 
-    json_extract_path_text('{"test" : {"key" : "tajo"}}','$.test.key');
+    select json_extract_path_text('{"test" : {"key" : "tajo"}}','$.test.key');
     > tajo
+
+.. function:: json_array_get (string json_array, int index)
+
+  Returns the element at the specified index into the JSON array. This function returns an element indexed from the end of an array with a negative index, and null if the element at the specified index doesn’t exist.
+
+  :param json_array: String of a JSON array
+  :param index: index
+  :rtype: text
+  :example:
+
+  .. code-block:: sql
+
+    select json_array_get('[100, 200, 300]', 0);
+    > 100
+
+    select json_array_get('[100, 200, 300]', -2);
+    > 200
+
+.. function:: json_array_contains (string json_array, any value)
+
+  Determine if the given value exists in the JSON array.
+
+  :param json_array: String of a JSON array
+  :param value: value of any type
+  :rtype: text
+  :example:
+
+  .. code-block:: sql
+
+    select json_array_contains('[100, 200, 300]', 100);
+    > t
+
+.. function:: json_array_length(string json_array)
+
+  Returns the length of json array.
+
+  :param json_array: String of a JSON array
+  :rtype: int8
+  :example:
+
+  .. code-block:: sql
+
+    select json_array_length('[100, 200, 300]');
+    > 3