Join side aliases should be optional

docs/ppl-lang/PPL-Example-Commands.md

@@ -298,7 +298,11 @@ source = table |  where ispresent(a) |
 - `source = table1 | left semi join left = l right = r on l.a = r.a table2`
 - `source = table1 | left anti join left = l right = r on l.a = r.a table2`
 - `source = table1 | join left = l right = r [ source = table2 | where d > 10 | head 5 ]`
-
+- `source = table1 | inner join on table1.a = table2.a table2 | fields table1.a, table2.a, table1.b, table1.c` (directly refer table name)
+- `source = table1 | inner join on a = c table2 | fields a, b, c, d` (ignore side aliases as long as no ambiguous)
+- `source = table1 as t1 | join left = l right = r on l.a = r.a table2 as t2 | fields l.a, r.a` (side alias overrides table alias)
+- `source = table1 as t1 | join left = l right = r on l.a = r.a table2 as t2 | fields t1.a, t2.a` (error, side alias overrides table alias)
+- `source = table1 | join left = l right = r on l.a = r.a [ source = table2 ] as s | fields l.a, s.a` (error, side alias overrides subquery alias)
 
 #### **Lookup**
 [See additional command details](ppl-lookup-command.md)

docs/ppl-lang/ppl-join-command.md

@@ -65,8 +65,8 @@ WHERE t1.serviceName = `order`
 SEARCH source=<left-table>
 | <other piped command>
 | [joinType] JOIN
-    leftAlias
-    rightAlias
+    [leftAlias]
+    [rightAlias]
     [joinHints]
     ON joinCriteria
     <right-table>
@@ -79,12 +79,12 @@ SEARCH source=<left-table>
 
 **leftAlias**
 - Syntax: `left = <leftAlias>`
-- Required
+- Optional
 - Description: The subquery alias to use with the left join side, to avoid ambiguous naming.
 
 **rightAlias**
 - Syntax: `right = <rightAlias>`
-- Required
+- Optional
 - Description: The subquery alias to use with the right join side, to avoid ambiguous naming.
 
 **joinHints**
@@ -138,11 +138,11 @@ Rewritten by PPL Join query:
 ```sql
 SEARCH source=customer
 | FIELDS c_custkey
-| LEFT OUTER JOIN left = c, right = o
-    ON c.c_custkey = o.o_custkey AND o_comment NOT LIKE '%unusual%packages%'
+| LEFT OUTER JOIN
+    ON c_custkey = o_custkey AND o_comment NOT LIKE '%unusual%packages%'
     orders
-| STATS count(o_orderkey) AS c_count BY c.c_custkey
-| STATS count(1) AS custdist BY c_count
+| STATS count(o_orderkey) AS c_count BY c_custkey
+| STATS count() AS custdist BY c_count
 | SORT - custdist, - c_count
 ```
 _- **Limitation: sub-searches is unsupported in join right side**_
@@ -151,14 +151,15 @@ If sub-searches is supported, above ppl query could be rewritten as:
 ```sql
 SEARCH source=customer
 | FIELDS c_custkey
-| LEFT OUTER JOIN left = c, right = o ON c.c_custkey = o.o_custkey
+| LEFT OUTER JOIN
+   ON c_custkey = o_custkey
    [
       SEARCH source=orders
       | WHERE o_comment NOT LIKE '%unusual%packages%'
       | FIELDS o_orderkey, o_custkey
    ]
-| STATS count(o_orderkey) AS c_count BY c.c_custkey
-| STATS count(1) AS custdist BY c_count
+| STATS count(o_orderkey) AS c_count BY c_custkey
+| STATS count() AS custdist BY c_count
 | SORT - custdist, - c_count
 ```
 

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

@@ -5,7 +5,7 @@
 
 package org.opensearch.flint.spark.ppl
 
-import org.apache.spark.sql.{QueryTest, Row}
+import org.apache.spark.sql.{AnalysisException, QueryTest, Row}
 import org.apache.spark.sql.catalyst.analysis.{UnresolvedAttribute, UnresolvedFunction, UnresolvedRelation, UnresolvedStar}
 import org.apache.spark.sql.catalyst.expressions.{Alias, And, Ascending, Divide, EqualTo, Floor, GreaterThan, LessThan, Literal, Multiply, Or, SortOrder}
 import org.apache.spark.sql.catalyst.plans.{Cross, Inner, LeftAnti, LeftOuter, LeftSemi, RightOuter}
@@ -924,4 +924,271 @@ class FlintSparkPPLJoinITSuite
       s
     }.size == 13)
   }
+
+  test("test multiple joins without table aliases") {
+    val frame = sql(s"""
+                       | source = $testTable1
+                       | | JOIN ON $testTable1.name = $testTable2.name $testTable2
+                       | | JOIN ON $testTable2.name = $testTable3.name $testTable3
+                       | | fields $testTable1.name, $testTable2.name, $testTable3.name
+                       | """.stripMargin)
+    assertSameRows(
+      Array(
+        Row("Jake", "Jake", "Jake"),
+        Row("Hello", "Hello", "Hello"),
+        Row("John", "John", "John"),
+        Row("David", "David", "David"),
+        Row("David", "David", "David"),
+        Row("Jane", "Jane", "Jane")),
+      frame)
+
+    val logicalPlan = frame.queryExecution.logical
+    val table1 = UnresolvedRelation(Seq("spark_catalog", "default", "flint_ppl_test1"))
+    val table2 = UnresolvedRelation(Seq("spark_catalog", "default", "flint_ppl_test2"))
+    val table3 = UnresolvedRelation(Seq("spark_catalog", "default", "flint_ppl_test3"))
+    val joinPlan1 = Join(
+      table1,
+      table2,
+      Inner,
+      Some(
+        EqualTo(
+          UnresolvedAttribute(s"$testTable1.name"),
+          UnresolvedAttribute(s"$testTable2.name"))),
+      JoinHint.NONE)
+    val joinPlan2 = Join(
+      joinPlan1,
+      table3,
+      Inner,
+      Some(
+        EqualTo(
+          UnresolvedAttribute(s"$testTable2.name"),
+          UnresolvedAttribute(s"$testTable3.name"))),
+      JoinHint.NONE)
+    val expectedPlan = Project(
+      Seq(
+        UnresolvedAttribute(s"$testTable1.name"),
+        UnresolvedAttribute(s"$testTable2.name"),
+        UnresolvedAttribute(s"$testTable3.name")),
+      joinPlan2)
+    comparePlans(expectedPlan, logicalPlan, checkAnalysis = false)
+  }
+
+  test("test multiple joins with part subquery aliases") {
+    val frame = sql(s"""
+                       | source = $testTable1
+                       | | JOIN left = t1 right = t2 ON t1.name = t2.name $testTable2
+                       | | JOIN right = t3 ON t1.name = t3.name $testTable3
+                       | | fields t1.name, t2.name, t3.name
+                       | """.stripMargin)
+    assertSameRows(
+      Array(
+        Row("Jake", "Jake", "Jake"),
+        Row("Hello", "Hello", "Hello"),
+        Row("John", "John", "John"),
+        Row("David", "David", "David"),
+        Row("David", "David", "David"),
+        Row("Jane", "Jane", "Jane")),
+      frame)
+
+    val logicalPlan = frame.queryExecution.logical
+    val table1 = UnresolvedRelation(Seq("spark_catalog", "default", "flint_ppl_test1"))
+    val table2 = UnresolvedRelation(Seq("spark_catalog", "default", "flint_ppl_test2"))
+    val table3 = UnresolvedRelation(Seq("spark_catalog", "default", "flint_ppl_test3"))
+    val joinPlan1 = Join(
+      SubqueryAlias("t1", table1),
+      SubqueryAlias("t2", table2),
+      Inner,
+      Some(EqualTo(UnresolvedAttribute("t1.name"), UnresolvedAttribute("t2.name"))),
+      JoinHint.NONE)
+    val joinPlan2 = Join(
+      joinPlan1,
+      SubqueryAlias("t3", table3),
+      Inner,
+      Some(EqualTo(UnresolvedAttribute("t1.name"), UnresolvedAttribute("t3.name"))),
+      JoinHint.NONE)
+    val expectedPlan = Project(
+      Seq(
+        UnresolvedAttribute("t1.name"),
+        UnresolvedAttribute("t2.name"),
+        UnresolvedAttribute("t3.name")),
+      joinPlan2)
+    comparePlans(expectedPlan, logicalPlan, checkAnalysis = false)
+  }
+
+  test("test multiple joins with self join 1") {
+    val frame = sql(s"""
+                       | source = $testTable1
+                       | | JOIN left = t1 right = t2 ON t1.name = t2.name $testTable2
+                       | | JOIN right = t3 ON t1.name = t3.name $testTable3
+                       | | JOIN right = t4 ON t1.name = t4.name $testTable1
+                       | | fields t1.name, t2.name, t3.name, t4.name
+                       | """.stripMargin)
+    assertSameRows(
+      Array(
+        Row("Jake", "Jake", "Jake", "Jake"),
+        Row("Hello", "Hello", "Hello", "Hello"),
+        Row("John", "John", "John", "John"),
+        Row("David", "David", "David", "David"),
+        Row("David", "David", "David", "David"),
+        Row("Jane", "Jane", "Jane", "Jane")),
+      frame)
+
+    val logicalPlan = frame.queryExecution.logical
+    val table1 = UnresolvedRelation(Seq("spark_catalog", "default", "flint_ppl_test1"))
+    val table2 = UnresolvedRelation(Seq("spark_catalog", "default", "flint_ppl_test2"))
+    val table3 = UnresolvedRelation(Seq("spark_catalog", "default", "flint_ppl_test3"))
+    val joinPlan1 = Join(
+      SubqueryAlias("t1", table1),
+      SubqueryAlias("t2", table2),
+      Inner,
+      Some(EqualTo(UnresolvedAttribute("t1.name"), UnresolvedAttribute("t2.name"))),
+      JoinHint.NONE)
+    val joinPlan2 = Join(
+      joinPlan1,
+      SubqueryAlias("t3", table3),
+      Inner,
+      Some(EqualTo(UnresolvedAttribute("t1.name"), UnresolvedAttribute("t3.name"))),
+      JoinHint.NONE)
+    val joinPlan3 = Join(
+      joinPlan2,
+      SubqueryAlias("t4", table1),
+      Inner,
+      Some(EqualTo(UnresolvedAttribute("t1.name"), UnresolvedAttribute("t4.name"))),
+      JoinHint.NONE)
+    val expectedPlan = Project(
+      Seq(
+        UnresolvedAttribute("t1.name"),
+        UnresolvedAttribute("t2.name"),
+        UnresolvedAttribute("t3.name"),
+        UnresolvedAttribute("t4.name")),
+      joinPlan3)
+    comparePlans(expectedPlan, logicalPlan, checkAnalysis = false)
+  }
+
+  test("test multiple joins with self join 2") {
+    val frame = sql(s"""
+                       | source = $testTable1
+                       | | JOIN left = t1 right = t2 ON t1.name = t2.name $testTable2
+                       | | JOIN right = t3 ON t1.name = t3.name $testTable3
+                       | | JOIN ON t1.name = t4.name
+                       |   [
+                       |     source = $testTable1
+                       |   ] as t4
+                       | | fields t1.name, t2.name, t3.name, t4.name
+                       | """.stripMargin)
+    assertSameRows(
+      Array(
+        Row("Jake", "Jake", "Jake", "Jake"),
+        Row("Hello", "Hello", "Hello", "Hello"),
+        Row("John", "John", "John", "John"),
+        Row("David", "David", "David", "David"),
+        Row("David", "David", "David", "David"),
+        Row("Jane", "Jane", "Jane", "Jane")),
+      frame)
+
+    val logicalPlan = frame.queryExecution.logical
+    val table1 = UnresolvedRelation(Seq("spark_catalog", "default", "flint_ppl_test1"))
+    val table2 = UnresolvedRelation(Seq("spark_catalog", "default", "flint_ppl_test2"))
+    val table3 = UnresolvedRelation(Seq("spark_catalog", "default", "flint_ppl_test3"))
+    val joinPlan1 = Join(
+      SubqueryAlias("t1", table1),
+      SubqueryAlias("t2", table2),
+      Inner,
+      Some(EqualTo(UnresolvedAttribute("t1.name"), UnresolvedAttribute("t2.name"))),
+      JoinHint.NONE)
+    val joinPlan2 = Join(
+      joinPlan1,
+      SubqueryAlias("t3", table3),
+      Inner,
+      Some(EqualTo(UnresolvedAttribute("t1.name"), UnresolvedAttribute("t3.name"))),
+      JoinHint.NONE)
+    val joinPlan3 = Join(
+      joinPlan2,
+      SubqueryAlias("t4", table1),
+      Inner,
+      Some(EqualTo(UnresolvedAttribute("t1.name"), UnresolvedAttribute("t4.name"))),
+      JoinHint.NONE)
+    val expectedPlan = Project(
+      Seq(
+        UnresolvedAttribute("t1.name"),
+        UnresolvedAttribute("t2.name"),
+        UnresolvedAttribute("t3.name"),
+        UnresolvedAttribute("t4.name")),
+      joinPlan3)
+    comparePlans(expectedPlan, logicalPlan, checkAnalysis = false)
+  }
+
+  test("check access the reference by aliases") {
+    var frame = sql(s"""
+                       | source = $testTable1
+                       | | JOIN left = t1 ON t1.name = t2.name $testTable2 as t2
+                       | | fields t1.name, t2.name
+                       | """.stripMargin)
+    assert(frame.collect().length > 0)
+
+    frame = sql(s"""
+                   | source = $testTable1 as t1
+                   | | JOIN ON t1.name = t2.name $testTable2 as t2
+                   | | fields t1.name, t2.name
+                   | """.stripMargin)
+    assert(frame.collect().length > 0)
+
+    frame = sql(s"""
+                   | source = $testTable1
+                   | | JOIN left = t1 ON t1.name = t2.name [ source = $testTable2 ] as t2
+                   | | fields t1.name, t2.name
+                   | """.stripMargin)
+    assert(frame.collect().length > 0)
+
+    frame = sql(s"""
+                   | source = $testTable1
+                   | | JOIN left = t1 ON t1.name = t2.name [ source = $testTable2 as t2 ]
+                   | | fields t1.name, t2.name
+                   | """.stripMargin)
+    assert(frame.collect().length > 0)
+  }
+
+  test("access the reference by override aliases should throw exception") {
+    var ex = intercept[AnalysisException](sql(s"""
+         | source = $testTable1
+         | | JOIN left = t1 right = t2 ON t1.name = t2.name $testTable2 as tt
+         | | fields tt.name
+         | """.stripMargin))
+    assert(ex.getMessage.contains("`tt`.`name` cannot be resolved"))
+
+    ex = intercept[AnalysisException](sql(s"""
+         | source = $testTable1 as tt
+         | | JOIN left = t1 right = t2 ON t1.name = t2.name $testTable2
+         | | fields tt.name
+         | """.stripMargin))
+    assert(ex.getMessage.contains("`tt`.`name` cannot be resolved"))
+
+    ex = intercept[AnalysisException](sql(s"""
+         | source = $testTable1
+         | | JOIN left = t1 right = t2 ON t1.name = t2.name [ source = $testTable2 as tt ]
+         | | fields tt.name
+         | """.stripMargin))
+    assert(ex.getMessage.contains("`tt`.`name` cannot be resolved"))
+
+    ex = intercept[AnalysisException](sql(s"""
+         | source = $testTable1
+         | | JOIN left = t1 ON t1.name = t2.name [ source = $testTable2 as tt ] as t2
+         | | fields tt.name
+         | """.stripMargin))
+    assert(ex.getMessage.contains("`tt`.`name` cannot be resolved"))
+
+    ex = intercept[AnalysisException](sql(s"""
+         | source = $testTable1
+         | | JOIN left = t1 right = t2 ON t1.name = t2.name [ source = $testTable2 ] as tt
+         | | fields tt.name
+         | """.stripMargin))
+    assert(ex.getMessage.contains("`tt`.`name` cannot be resolved"))
+
+    ex = intercept[AnalysisException](sql(s"""
+         | source = $testTable1 as tt
+         | | JOIN left = t1 ON t1.name = t2.name $testTable2 as t2
+         | | fields tt.name
+         | """.stripMargin))
+    assert(ex.getMessage.contains("`tt`.`name` cannot be resolved"))
+  }
 }

ppl-spark-integration/src/main/antlr4/OpenSearchPPLParser.g4

@@ -326,7 +326,7 @@ joinType
    ;
 
 sideAlias
-   : LEFT EQUAL leftAlias = ident COMMA? RIGHT EQUAL rightAlias = ident
+   : (LEFT EQUAL leftAlias = ident)? COMMA? (RIGHT EQUAL rightAlias = ident)?
    ;
 
 joinCriteria

ppl-spark-integration/src/main/java/org/opensearch/sql/ast/tree/DescribeRelation.java

@@ -8,12 +8,14 @@
 import lombok.ToString;
 import org.opensearch.sql.ast.expression.UnresolvedExpression;
 
+import java.util.Collections;
+
 /**
  * Extend Relation to describe the table itself
  */
 @ToString
 public class DescribeRelation extends Relation{
     public DescribeRelation(UnresolvedExpression tableName) {
-        super(tableName);
+        super(Collections.singletonList(tableName));
     }
 }

ppl-spark-integration/src/main/java/org/opensearch/sql/ast/tree/Join.java

@@ -25,15 +25,15 @@
 public class Join extends UnresolvedPlan {
     private UnresolvedPlan left;
     private final UnresolvedPlan right;
-    private final String leftAlias;
-    private final String rightAlias;
+    private final Optional<String> leftAlias;
+    private final Optional<String> rightAlias;
     private final JoinType joinType;
     private final Optional<UnresolvedExpression> joinCondition;
     private final JoinHint joinHint;
 
     @Override
     public UnresolvedPlan attach(UnresolvedPlan child) {
-        this.left = new SubqueryAlias(leftAlias, child);
+        this.left = leftAlias.isEmpty() ? child : new SubqueryAlias(leftAlias.get(), child);
         return this;
     }