[CALCITE-7547] BIG_QUERY should allow field access on UNNEST of struct array AS alias

core/src/main/java/org/apache/calcite/sql/validate/SqlConformance.java

@@ -375,6 +375,7 @@ default boolean isColonFieldAccessAllowed() {
    * fields of T if T is a STRUCT type.
    *
    * <p>Among the built-in conformance levels, true in
+   * {@link SqlConformanceEnum#BIG_QUERY},
    * {@link SqlConformanceEnum#PRESTO};
    * false otherwise.
    */

core/src/main/java/org/apache/calcite/sql/validate/SqlConformanceEnum.java

@@ -435,6 +435,7 @@ public enum SqlConformanceEnum implements SqlConformance {
 
   @Override public boolean allowAliasUnnestItems() {
     switch (this) {
+    case BIG_QUERY:
     case PRESTO:
       return true;
     default:

core/src/test/java/org/apache/calcite/test/SqlToRelConverterTest.java

@@ -1939,6 +1939,32 @@ public static void checkActualAndReferenceFiles() {
     sql(sql).withConformance(SqlConformanceEnum.PRESTO).ok();
   }
 
+  /**
+   * Test case for
+   * <a href="https://issues.apache.org/jira/browse/CALCITE-7547">[CALCITE-7547]
+   * BIG_QUERY conformance should allow field access on
+   * UNNEST(array_of_struct) AS alias</a>.
+   */
+  @Test void testAliasUnnestArrayPlanWithSingleColumnBigQuery() {
+    final String sql = "select d.deptno, employee.empno\n"
+        + "from dept_nested_expanded as d,\n"
+        + " UNNEST(d.employees) as t(employee)";
+    sql(sql).withConformance(SqlConformanceEnum.BIG_QUERY).ok();
+  }
+
+  /**
+   * Test case for
+   * <a href="https://issues.apache.org/jira/browse/CALCITE-7547">[CALCITE-7547]
+   * BIG_QUERY conformance should allow field access on
+   * UNNEST(array_of_struct) AS alias</a>.
+   */
+  @Test void testAliasUnnestArrayPlanWithDoubleColumnBigQuery() {
+    final String sql = "select d.deptno, e, k.empno\n"
+        + "from dept_nested_expanded as d CROSS JOIN\n"
+        + " UNNEST(d.admins, d.employees) as t(e, k)";
+    sql(sql).withConformance(SqlConformanceEnum.BIG_QUERY).ok();
+  }
+
   @Test void testArrayOfRecord() {
     sql("select employees[1].detail.skills[2+3].desc from dept_nested").ok();
   }

core/src/test/java/org/apache/calcite/test/SqlValidatorTest.java

@@ -8816,6 +8816,37 @@ void testGroupExpressionEquivalenceParams() {
             + "\\('EMPNO', 'ENAME', 'DETAIL'\\), whereas alias list has 1 columns");
   }
 
+  /**
+   * Test case for
+   * <a href="https://issues.apache.org/jira/browse/CALCITE-7547">[CALCITE-7547]
+   * BIG_QUERY conformance should allow field access on
+   * UNNEST(array_of_struct) AS alias</a>.
+   */
+  @Test void testAliasUnnestMultipleArraysBigQuery() {
+    // for accessing a field in STRUCT type unnested from array
+    sql("select e.ENAME\n"
+        + "from dept_nested_expanded as d CROSS JOIN\n"
+        + " UNNEST(d.employees) as t(e)")
+        .withConformance(SqlConformanceEnum.BIG_QUERY).columnType("VARCHAR(10) NOT NULL");
+
+    // for unnesting multiple arrays at the same time
+    sql("select d.deptno, e, k.empno, l.\"unit\", l.\"X\" * l.\"Y\"\n"
+        + "from dept_nested_expanded as d CROSS JOIN\n"
+        + " UNNEST(d.admins, d.employees, d.offices) as t(e, k, l)")
+        .withConformance(SqlConformanceEnum.BIG_QUERY).ok();
+
+    // Make sure validation fails properly given illegal select items
+    sql("select d.deptno, ^e^.some_column, k.empno\n"
+        + "from dept_nested_expanded as d CROSS JOIN\n"
+        + " UNNEST(d.admins, d.employees) as t(e, k)")
+        .withConformance(SqlConformanceEnum.BIG_QUERY)
+        .fails("Table 'E' not found");
+    sql("select d.deptno, e.detail, ^unknown^.detail\n"
+        + "from dept_nested_expanded as d CROSS JOIN\n"
+        + " UNNEST(d.employees) as t(e)")
+        .withConformance(SqlConformanceEnum.BIG_QUERY).fails("Incompatible types");
+  }
+
   @Test void testUnnestArray() {
     sql("select*from unnest(array[1])")
         .columnType("INTEGER NOT NULL");

core/src/test/resources/org/apache/calcite/test/SqlToRelConverterTest.xml

@@ -341,6 +341,23 @@ LogicalProject(DEPTNO=[$0], E=[$5], EMPNO=[$6.EMPNO])
     </Resource>
     <Resource name="sql">
       <![CDATA[select d.deptno, e, k.empno
+from dept_nested_expanded as d CROSS JOIN
+ UNNEST(d.admins, d.employees) as t(e, k)]]>
+    </Resource>
+  </TestCase>
+  <TestCase name="testAliasUnnestArrayPlanWithDoubleColumnBigQuery">
+    <Resource name="plan">
+      <![CDATA[
+LogicalProject(DEPTNO=[$0], E=[$5], EMPNO=[$6.EMPNO])
+  LogicalCorrelate(correlation=[$cor0], joinType=[inner], requiredColumns=[{2, 3}])
+    LogicalTableScan(table=[[CATALOG, SALES, DEPT_NESTED_EXPANDED]])
+    Uncollect
+      LogicalProject(ADMINS=[$cor0.ADMINS], EMPLOYEES=[$cor0.EMPLOYEES])
+        LogicalValues(tuples=[[{ 0 }]])
+]]>
+    </Resource>
+    <Resource name="sql">
+      <![CDATA[select d.deptno, e, k.empno
 from dept_nested_expanded as d CROSS JOIN
  UNNEST(d.admins, d.employees) as t(e, k)]]>
     </Resource>
@@ -358,6 +375,23 @@ LogicalProject(DEPTNO=[$0], EMPNO=[$5.EMPNO])
     </Resource>
     <Resource name="sql">
       <![CDATA[select d.deptno, employee.empno
+from dept_nested_expanded as d,
+ UNNEST(d.employees) as t(employee)]]>
+    </Resource>
+  </TestCase>
+  <TestCase name="testAliasUnnestArrayPlanWithSingleColumnBigQuery">
+    <Resource name="plan">
+      <![CDATA[
+LogicalProject(DEPTNO=[$0], EMPNO=[$5.EMPNO])
+  LogicalCorrelate(correlation=[$cor0], joinType=[inner], requiredColumns=[{2}])
+    LogicalTableScan(table=[[CATALOG, SALES, DEPT_NESTED_EXPANDED]])
+    Uncollect
+      LogicalProject(EMPLOYEES=[$cor0.EMPLOYEES])
+        LogicalValues(tuples=[[{ 0 }]])
+]]>
+    </Resource>
+    <Resource name="sql">
+      <![CDATA[select d.deptno, employee.empno
 from dept_nested_expanded as d,
  UNNEST(d.employees) as t(employee)]]>
     </Resource>