[CALCITE-933] Add null check in RelBuilder.scan() and throw a nice ex…

core/src/main/java/org/apache/calcite/runtime/CalciteResource.java

@@ -591,6 +591,9 @@ ExInst<CalciteException> illegalArgumentForTableFunctionCall(String a0,
 
   @BaseMessage("View is not modifiable. No value is supplied for NOT NULL column ''{0}'' of base table ''{1}''")
   ExInst<SqlValidatorException> noValueSuppliedForViewColumn(String columnName, String tableName);
+
+  @BaseMessage("Table ''{0}'' not found")
+  ExInst<CalciteException> tableNotFound(String tableName);
 }
 
 // End CalciteResource.java

core/src/main/java/org/apache/calcite/tools/RelBuilder.java

@@ -45,19 +45,17 @@
 import org.apache.calcite.rex.RexLiteral;
 import org.apache.calcite.rex.RexNode;
 import org.apache.calcite.rex.RexUtil;
+import org.apache.calcite.runtime.CalciteException;
+import org.apache.calcite.runtime.Resources;
 import org.apache.calcite.schema.SchemaPlus;
 import org.apache.calcite.server.CalciteServerStatement;
 import org.apache.calcite.sql.SqlAggFunction;
 import org.apache.calcite.sql.SqlKind;
 import org.apache.calcite.sql.SqlOperator;
 import org.apache.calcite.sql.fun.SqlStdOperatorTable;
 import org.apache.calcite.sql.type.SqlTypeName;
-import org.apache.calcite.util.ImmutableBitSet;
-import org.apache.calcite.util.ImmutableIntList;
-import org.apache.calcite.util.NlsString;
-import org.apache.calcite.util.Pair;
-import org.apache.calcite.util.Stacks;
-import org.apache.calcite.util.Util;
+import org.apache.calcite.sql.validate.SqlValidatorException;
+import org.apache.calcite.util.*;
 import org.apache.calcite.util.mapping.Mapping;
 import org.apache.calcite.util.mapping.Mappings;
 
@@ -650,6 +648,9 @@ public AggCall max(String alias, RexNode operand) {
   public RelBuilder scan(String tableName) {
     final RelOptTable relOptTable =
         relOptSchema.getTableForMember(ImmutableList.of(tableName));
+    if (relOptTable == null) {
+      throw Static.RESOURCE.tableNotFound(tableName).ex();
+    }
     final RelNode scan = scanFactory.createScan(cluster, relOptTable);
     push(scan);
     return this;

core/src/main/resources/org/apache/calcite/runtime/CalciteResource.properties

@@ -193,4 +193,5 @@ CannotStreamValues=Cannot stream VALUES
 ModifiableViewMustBeBasedOnSingleTable=Modifiable view must be based on a single table
 MoreThanOneMappedColumn=View is not modifiable. More than one expression maps to column ''{0}'' of base table ''{1}''
 NoValueSuppliedForViewColumn=View is not modifiable. No value is supplied for NOT NULL column ''{0}'' of base table ''{1}''
+TableNotFound=Table ''{0}'' not found
 # End CalciteResource.properties

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

@@ -116,6 +116,36 @@ private String str(RelNode r) {
         is("LogicalTableScan(table=[[scott, EMP]])\n"));
   }
 
+  @Test public void testScanInvalidTable() {
+    // Equivalent SQL:
+    //   SELECT *
+    //   FROM zzz
+    try {
+      final RelNode root =
+          RelBuilder.create(config().build())
+              .scan("ZZZ") // this relation does not exist
+              .build();
+      fail("Expected error because ZZZ does not exist");
+    } catch (Exception e) {
+      assertThat(e.getMessage(), is("Table 'ZZZ' not found"));
+    }
+  }
+
+  @Test public void testScanValidTableWrongCase() {
+    // Equivalent SQL:
+    //   SELECT *
+    //   FROM emp
+    try {
+      final RelNode root =
+          RelBuilder.create(config().build())
+              .scan("emp") // the table is named 'EMP', not 'emp'
+              .build();
+      fail("Table names are case-sensitive and scan of 'emp' should have failed");
+    } catch (Exception e) {
+      assertThat(e.getMessage(), is("Table 'emp' not found"));
+    }
+  }
+
   @Test public void testScanFilterTrue() {
     // Equivalent SQL:
     //   SELECT *