Translate PPL LOOKUP Command

docs/PPL-Lookup-command.md

@@ -0,0 +1,69 @@
+## PPL Lookup Command
+
+## Overview
+Lookup command enriches your search data by adding or replacing data from a lookup index (dimension table).
+You can extend fields of an index with values from a dimension table, append or replace values when lookup condition is matched.
+As an alternative of [Join command](../docs/PPL-Join-command.md), lookup command is more suitable for enriching the source data with a static dataset.
+
+
+### Syntax of Lookup Command
+
+```sql
+SEARCH source=<sourceIndex>
+| <other piped command>
+| LOOKUP <lookupIndex> (<lookupMappingField> [AS <sourceMappingField>])...
+    [(REPLACE | APPEND) (<inputField> [AS <outputField>])...]
+| <other piped command>
+```
+**lookupIndex**
+- Required
+- Description: the name of lookup index (dimension table)
+
+**lookupMappingField**
+- Required
+- Description: A mapping key in \<lookupIndex\>, analogy to a join key from right table. You can specify multiple \<lookupMappingField\> with comma-delimited.
+
+**sourceMappingField**
+- Optional
+- Default: \<lookupMappingField\>
+- Description: A mapping key from source **query**, analogy to a join key from left side. If you don't specify any \<sourceMappingField\>, its default value is \<lookupMappingField\>.
+
+**inputField**
+- Optional
+- Default: All fields of \<lookupIndex\> where matched values are applied to result output if no field is specified.
+- Description: A field in \<lookupIndex\> where matched values are applied to result output. You can specify multiple \<inputField\> with comma-delimited. If you don't specify any \<inputField\>, all fields of \<lookupIndex\> where matched values are applied to result output.
+
+**outputField**
+- Optional
+- Default: \<inputField\>
+- Description:  A field of output. You can specify multiple \<outputField\>. If you specify \<outputField\> with an existing field name in source query, its values will be replaced or appended by matched values from \<inputField\>. If the field specified in \<outputField\> is a new field, an extended new field will be applied to the results.
+
+**REPLACE | APPEND**
+- Optional
+- Default: REPLACE
+- Description: If you specify REPLACE, matched values in \<lookupIndex\> field overwrite the values in result. If you specify APPEND, matched values in \<lookupIndex\> field only append to the missing values in result.
+
+### Usage
+> LOOKUP <lookupIndex> id AS cid REPLACE mail AS email</br>
+> LOOKUP <lookupIndex> name REPLACE mail AS email</br>
+> LOOKUP <lookupIndex> id AS cid, name APPEND address, mail AS email</br>
+> LOOKUP <lookupIndex> id</br>
+
+### Example
+```sql
+SEARCH source=<sourceIndex>
+| WHERE orderType = 'Cancelled'
+| LOOKUP account_list, mkt_id AS mkt_code REPLACE amount, account_name AS name
+| STATS count(mkt_code), avg(amount) BY name
+```
+```sql
+SEARCH source=<sourceIndex>
+| DEDUP market_id
+| EVAL category=replace(category, "-", ".")
+| EVAL category=ltrim(category, "dvp.")
+| LOOKUP bounce_category category AS category APPEND classification
+```
+```sql
+SEARCH source=<sourceIndex>
+| LOOKUP bounce_category category
+```

integ-test/src/integration/scala/org/opensearch/flint/spark/FlintSparkSuite.scala

@@ -277,6 +277,54 @@ trait FlintSparkSuite extends QueryTest with FlintSuite with OpenSearchSuite wit
          | """.stripMargin)
   }
 
+  protected def createPeopleTable(testTable: String): Unit = {
+    sql(s"""
+           | CREATE TABLE $testTable
+           | (
+           |   id INT,
+           |   name STRING,
+           |   occupation STRING,
+           |   country STRING,
+           |   salary INT
+           | )
+           | USING $tableType $tableOptions
+           |""".stripMargin)
+
+    // Insert data into the new table
+    sql(s"""
+           | INSERT INTO $testTable
+           | VALUES (1000, 'Jake', 'Engineer', 'England' , 100000),
+           |        (1001, 'Hello', 'Artist', 'USA', 70000),
+           |        (1002, 'John', 'Doctor', 'Canada', 120000),
+           |        (1003, 'David', 'Doctor', null, 120000),
+           |        (1004, 'David', null, 'Canada', 0),
+           |        (1005, 'Jane', 'Scientist', 'Canada', 90000)
+           | """.stripMargin)
+  }
+
+  protected def createWorkInformationTable(testTable: String): Unit = {
+    sql(s"""
+           | CREATE TABLE $testTable
+           | (
+           |   uid INT,
+           |   name STRING,
+           |   department STRING,
+           |   occupation STRING
+           | )
+           | USING $tableType $tableOptions
+           |""".stripMargin)
+
+    // Insert data into the new table
+    sql(s"""
+           | INSERT INTO $testTable
+           | VALUES (1000, 'Jake', 'IT', 'Engineer'),
+           |        (1002, 'John', 'DATA', 'Scientist'),
+           |        (1003, 'David', 'HR', 'Doctor'),
+           |        (1005, 'Jane', 'DATA', 'Engineer'),
+           |        (1006, 'Tom', 'SALES', 'Artist')
+           | """.stripMargin)
+  }
+
   protected def createOccupationTopRareTable(testTable: String): Unit = {
     sql(s"""
       | CREATE TABLE $testTable