fix: allow getting metadata without calling next() (#1691)

* fix: allow getting metadata without calling next()

DirectExecuteResultSet, which is used in the Connection API, directly
executes any query that it is given without the need to call
ResultSet.next() first. This also makes it possible to get the ResultSet
metadata from the result without the need to calling ResultSet.next()
first.

* fix: add methods to exclude list for test

Author: olavloite

google-cloud-spanner/src/main/java/com/google/cloud/spanner/connection/DirectExecuteResultSet.java

@@ -96,31 +96,26 @@ public ResultSetStats getStats() {
 
   @Override
   public Type getType() {
-    Preconditions.checkState(nextCalledByClient, MISSING_NEXT_CALL);
     return delegate.getType();
   }
 
   @Override
   public int getColumnCount() {
-    Preconditions.checkState(nextCalledByClient, MISSING_NEXT_CALL);
     return delegate.getColumnCount();
   }
 
   @Override
   public int getColumnIndex(String columnName) {
-    Preconditions.checkState(nextCalledByClient, MISSING_NEXT_CALL);
     return delegate.getColumnIndex(columnName);
   }
 
   @Override
   public Type getColumnType(int columnIndex) {
-    Preconditions.checkState(nextCalledByClient, MISSING_NEXT_CALL);
     return delegate.getColumnType(columnIndex);
   }
 
   @Override
   public Type getColumnType(String columnName) {
-    Preconditions.checkState(nextCalledByClient, MISSING_NEXT_CALL);
     return delegate.getColumnType(columnName);
   }
 

google-cloud-spanner/src/test/java/com/google/cloud/spanner/connection/DirectExecuteResultSetTest.java

@@ -53,7 +53,17 @@ private DirectExecuteResultSet createSubject() {
   public void testMethodCallBeforeNext()
       throws IllegalAccessException, IllegalArgumentException, InvocationTargetException {
     List<String> excludedMethods =
-        Arrays.asList("getStats", "next", "close", "ofResultSet", "equals", "hashCode");
+        Arrays.asList(
+            "getStats",
+            "next",
+            "close",
+            "ofResultSet",
+            "equals",
+            "hashCode",
+            "getType",
+            "getColumnCount",
+            "getColumnIndex",
+            "getColumnType");
     DirectExecuteResultSet subject = createSubject();
     callMethods(subject, excludedMethods, IllegalStateException.class);
   }

google-cloud-spanner/src/test/java/com/google/cloud/spanner/connection/it/ITReadOnlySpannerTest.java

@@ -33,6 +33,7 @@
 import com.google.cloud.spanner.ResultSet;
 import com.google.cloud.spanner.SpannerException;
 import com.google.cloud.spanner.Statement;
+import com.google.cloud.spanner.Type;
 import com.google.cloud.spanner.connection.ITAbstractSpannerTest;
 import com.google.cloud.spanner.connection.SqlScriptVerifier;
 import java.math.BigInteger;
@@ -213,4 +214,28 @@ public void testMultipleOpenResultSets() throws InterruptedException {
       rs2.close();
     }
   }
+
+  @Test
+  public void testGetMetadataFromAnalyzeQuery() {
+    assumeFalse("analyze query is not supported on the emulator", isUsingEmulator());
+    try (ITConnection connection = createConnection()) {
+      // Request a query plan without executing the query and verify that we can get the column
+      // metadata of the query without calling resultSet.next() first.
+      try (ResultSet resultSet =
+          connection.analyzeQuery(
+              Statement.of("SELECT number, name FROM NUMBERS"), QueryAnalyzeMode.PLAN)) {
+        assertEquals(2, resultSet.getColumnCount());
+
+        assertEquals(0, resultSet.getColumnIndex("number"));
+        assertEquals("number", resultSet.getType().getStructFields().get(0).getName());
+        assertEquals(Type.int64(), resultSet.getColumnType(0));
+        assertEquals(Type.int64(), resultSet.getColumnType("number"));
+
+        assertEquals(1, resultSet.getColumnIndex("name"));
+        assertEquals("name", resultSet.getType().getStructFields().get(1).getName());
+        assertEquals(Type.string(), resultSet.getColumnType(1));
+        assertEquals(Type.string(), resultSet.getColumnType("name"));
+      }
+    }
+  }
 }