The flatten command implemented

Signed-off-by: Lukasz Soszynski <lukasz.soszynski@eliatra.com>
opensearch-project · Oct 29, 2024 · 955ffe3 · 955ffe3
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diff --git a/docs/ppl-lang/PPL-Example-Commands.md b/docs/ppl-lang/PPL-Example-Commands.md
@@ -117,6 +117,14 @@ Assumptions: `a`, `b`, `c`, `d`, `e` are existing fields in `table`
 - `source = table | fillnull using a = 101, b = 102`
 - `source = table | fillnull using a = concat(b, c), d = 2 * pi() * e`
 
+### Flatten
+Assumptions: `bridges`, `coor` are existing fields in `table`, and the field's types are `struct<?,?>` or `array<struct<?,?>>`  
+- `source = table | flatten bridges`
+- `source = table | flatten coor`
+- `source = table | flatten bridges | flatten coor`
+- `source = table | fields bridges | flatten bridges`
+- `source = table | fields country, bridges | flatten bridges | fields country, length | stats avg(length) as avg by country`
+
 ```sql
 source = table | eval e = eval status_category =
         case(a >= 200 AND a < 300, 'Success',

diff --git a/docs/ppl-lang/README.md b/docs/ppl-lang/README.md
@@ -31,6 +31,8 @@ For additional examples see the next [documentation](PPL-Example-Commands.md).
     - [`describe command`](PPL-Example-Commands.md/#describe)
 
     - [`fillnull command`](ppl-fillnull-command.md)
+
+    - [`flatten command`](ppl-flatten-command.md)
 
     - [`eval command`](ppl-eval-command.md)
 

diff --git a/docs/ppl-lang/ppl-flatten-command.md b/docs/ppl-lang/ppl-flatten-command.md
@@ -0,0 +1,90 @@
+## PPL `flatten` command
+
+### Description
+Using `flatten` command to flatten a field of type:
+- `struct<?,?>`
+- `array<struct<?,?>>`
+
+
+### Syntax
+`flatten <field>`
+
+* field: to be flattened. The field must be of supported type.
+
+### Test table
+#### Schema
+| col\_name | data\_type                                      |
+|-----------|-------------------------------------------------|
+| \_time    | string                                          |
+| bridges   | array\<struct\<length:bigint,name:string\>\>    |
+| city      | string                                          |
+| coor      | struct\<alt:bigint,lat:double,long:double\>     |
+| country   | string                                          |
+#### Data
+| \_time              | bridges                                      | city    | coor                   | country       |
+|---------------------|----------------------------------------------|---------|------------------------|---------------|
+| 2024-09-13T12:00:00 | [{801, Tower Bridge}, {928, London Bridge}]  | London  | {35, 51.5074, -0.1278} | England       |
+| 2024-09-13T12:00:00 | [{232, Pont Neuf}, {160, Pont Alexandre III}]| Paris   | {35, 48.8566, 2.3522}  | France        |
+| 2024-09-13T12:00:00 | [{48, Rialto Bridge}, {11, Bridge of Sighs}] | Venice  | {2, 45.4408, 12.3155}  | Italy         |
+| 2024-09-13T12:00:00 | [{516, Charles Bridge}, {343, Legion Bridge}]| Prague  | {200, 50.0755, 14.4378}| Czech Republic|
+| 2024-09-13T12:00:00 | [{375, Chain Bridge}, {333, Liberty Bridge}] | Budapest| {96, 47.4979, 19.0402} | Hungary       |
+| 1990-09-13T12:00:00 | NULL                                         | Warsaw  | NULL                   | Poland        |
+
+
+
+### Example 1: flatten struct
+This example shows how to flatten a struct field.
+PPL query:
+    - `source=table | flatten coor`
+
+| \_time              | bridges                                      | city    | country       | alt | lat    | long   |
+|---------------------|----------------------------------------------|---------|---------------|-----|--------|--------|
+| 2024-09-13T12:00:00 | [{801, Tower Bridge}, {928, London Bridge}]  | London  | England       | 35  | 51.5074| -0.1278|
+| 2024-09-13T12:00:00 | [{232, Pont Neuf}, {160, Pont Alexandre III}]| Paris   | France        | 35  | 48.8566| 2.3522 |
+| 2024-09-13T12:00:00 | [{48, Rialto Bridge}, {11, Bridge of Sighs}] | Venice  | Italy         | 2   | 45.4408| 12.3155|
+| 2024-09-13T12:00:00 | [{516, Charles Bridge}, {343, Legion Bridge}]| Prague  | Czech Republic| 200 | 50.0755| 14.4378|
+| 2024-09-13T12:00:00 | [{375, Chain Bridge}, {333, Liberty Bridge}] | Budapest| Hungary       | 96  | 47.4979| 19.0402|
+| 1990-09-13T12:00:00 | NULL                                         | Warsaw  | Poland        | NULL| NULL   | NULL   |
+
+
+
+### Example 2: flatten array
+
+The example shows how to flatten an array of struct fields.
+
+PPL query:
+    - `source=table | flatten bridges`
+
+| \_time              | city    | coor                   | country       | length | name              |
+|---------------------|---------|------------------------|---------------|--------|-------------------|
+| 2024-09-13T12:00:00 | London  | {35, 51.5074, -0.1278} | England       | 801    | Tower Bridge      |
+| 2024-09-13T12:00:00 | London  | {35, 51.5074, -0.1278} | England       | 928    | London Bridge     |
+| 2024-09-13T12:00:00 | Paris   | {35, 48.8566, 2.3522}  | France        | 232    | Pont Neuf         |
+| 2024-09-13T12:00:00 | Paris   | {35, 48.8566, 2.3522}  | France        | 160    | Pont Alexandre III|
+| 2024-09-13T12:00:00 | Venice  | {2, 45.4408, 12.3155}  | Italy         | 48     | Rialto Bridge     |
+| 2024-09-13T12:00:00 | Venice  | {2, 45.4408, 12.3155}  | Italy         | 11     | Bridge of Sighs   |
+| 2024-09-13T12:00:00 | Prague  | {200, 50.0755, 14.4378}| Czech Republic| 516    | Charles Bridge    |
+| 2024-09-13T12:00:00 | Prague  | {200, 50.0755, 14.4378}| Czech Republic| 343    | Legion Bridge     |
+| 2024-09-13T12:00:00 | Budapest| {96, 47.4979, 19.0402} | Hungary       | 375    | Chain Bridge      |
+| 2024-09-13T12:00:00 | Budapest| {96, 47.4979, 19.0402} | Hungary       | 333    | Liberty Bridge    |
+| 1990-09-13T12:00:00 | Warsaw  | NULL                   | Poland        | NULL   | NULL              |
+
+
+### Example 3: flatten array and struct
+This example shows how to flatten multiple fields.
+PPL query:
+    - `source=table | flatten bridges | flatten coor`
+
+| \_time              | city    | country       | length | name              | alt  | lat    | long   |
+|---------------------|---------|---------------|--------|-------------------|------|--------|--------|
+| 2024-09-13T12:00:00 | London  | England       | 801    | Tower Bridge      | 35   | 51.5074| -0.1278|
+| 2024-09-13T12:00:00 | London  | England       | 928    | London Bridge     | 35   | 51.5074| -0.1278|
+| 2024-09-13T12:00:00 | Paris   | France        | 232    | Pont Neuf         | 35   | 48.8566| 2.3522 |
+| 2024-09-13T12:00:00 | Paris   | France        | 160    | Pont Alexandre III| 35   | 48.8566| 2.3522 |
+| 2024-09-13T12:00:00 | Venice  | Italy         | 48     | Rialto Bridge     | 2    | 45.4408| 12.3155|
+| 2024-09-13T12:00:00 | Venice  | Italy         | 11     | Bridge of Sighs   | 2    | 45.4408| 12.3155|
+| 2024-09-13T12:00:00 | Prague  | Czech Republic| 516    | Charles Bridge    | 200  | 50.0755| 14.4378|
+| 2024-09-13T12:00:00 | Prague  | Czech Republic| 343    | Legion Bridge     | 200  | 50.0755| 14.4378|
+| 2024-09-13T12:00:00 | Budapest| Hungary       | 375    | Chain Bridge      | 96   | 47.4979| 19.0402|
+| 2024-09-13T12:00:00 | Budapest| Hungary       | 333    | Liberty Bridge    | 96   | 47.4979| 19.0402|
+| 1990-09-13T12:00:00 | Warsaw  | Poland        | NULL   | NULL              | NULL | NULL   | NULL   |
diff --git a/integ-test/src/integration/scala/org/opensearch/flint/spark/FlintSparkSuite.scala b/integ-test/src/integration/scala/org/opensearch/flint/spark/FlintSparkSuite.scala
@@ -5,7 +5,7 @@
 
 package org.opensearch.flint.spark
 
-import java.nio.file.{Files, Paths}
+import java.nio.file.{Files, Path, Paths}
 import java.util.Comparator
 import java.util.concurrent.{ScheduledExecutorService, ScheduledFuture}
 
@@ -669,4 +669,100 @@ trait FlintSparkSuite extends QueryTest with FlintSuite with OpenSearchSuite wit
            |        (11, null, false)
            | """.stripMargin)
   }
+
+  protected def createSimpleNestedJsonContentTable(tempFile: Path, testTable: String): Unit = {
+    val json =
+      """
+        |[
+        |  {
+        |    "_time": "2024-09-13T12:00:00",
+        |    "bridges": [
+        |      {"name": "Tower Bridge", "length": 801},
+        |      {"name": "London Bridge", "length": 928}
+        |    ],
+        |    "city": "London",
+        |    "country": "England",
+        |    "coor": {
+        |      "lat": 51.5074,
+        |      "long": -0.1278,
+        |      "alt": 35
+        |    }
+        |  },
+        |  {
+        |    "_time": "2024-09-13T12:00:00",
+        |    "bridges": [
+        |      {"name": "Pont Neuf", "length": 232},
+        |      {"name": "Pont Alexandre III", "length": 160}
+        |    ],
+        |    "city": "Paris",
+        |    "country": "France",
+        |    "coor": {
+        |      "lat": 48.8566,
+        |      "long": 2.3522,
+        |      "alt": 35
+        |    }
+        |  },
+        |  {
+        |    "_time": "2024-09-13T12:00:00",
+        |    "bridges": [
+        |      {"name": "Rialto Bridge", "length": 48},
+        |      {"name": "Bridge of Sighs", "length": 11}
+        |    ],
+        |    "city": "Venice",
+        |    "country": "Italy",
+        |    "coor": {
+        |      "lat": 45.4408,
+        |      "long": 12.3155,
+        |      "alt": 2
+        |    }
+        |  },
+        |  {
+        |    "_time": "2024-09-13T12:00:00",
+        |    "bridges": [
+        |      {"name": "Charles Bridge", "length": 516},
+        |      {"name": "Legion Bridge", "length": 343}
+        |    ],
+        |    "city": "Prague",
+        |    "country": "Czech Republic",
+        |    "coor": {
+        |      "lat": 50.0755,
+        |      "long": 14.4378,
+        |      "alt": 200
+        |    }
+        |  },
+        |  {
+        |    "_time": "2024-09-13T12:00:00",
+        |    "bridges": [
+        |      {"name": "Chain Bridge", "length": 375},
+        |      {"name": "Liberty Bridge", "length": 333}
+        |    ],
+        |    "city": "Budapest",
+        |    "country": "Hungary",
+        |    "coor": {
+        |      "lat": 47.4979,
+        |      "long": 19.0402,
+        |      "alt": 96
+        |    }
+        |  },
+        |  {
+        |    "_time": "1990-09-13T12:00:00",
+        |    "bridges": null,
+        |    "city": "Warsaw",
+        |    "country": "Poland",
+        |    "coor": null
+        |  }
+        |]
+        |""".stripMargin
+    val tempFile = Files.createTempFile("jsonTestData", ".json")
+    val absolutPath = tempFile.toAbsolutePath.toString;
+    Files.write(tempFile, json.getBytes)
+    sql(s"""
+         | CREATE TEMPORARY VIEW $testTable
+         | USING org.apache.spark.sql.json
+         | OPTIONS (
+         |  path "$absolutPath",
+         |  multiLine true
+         | );
+         |""".stripMargin)
+  }
 }