feat: report whether column is generated in JDBC metadata (#291)

Cloud Spanner now supports generated columns. These were reported as normal columns
in the JDBC metadata. These are now reported correctly as generated columns.

Fixes #290

Author: olavloite

src/main/resources/com/google/cloud/spanner/jdbc/DatabaseMetaData_GetColumns.sql

@@ -72,7 +72,10 @@ SELECT TABLE_CATALOG AS TABLE_CAT, TABLE_SCHEMA AS TABLE_SCHEM, TABLE_NAME, COLU
   NULL AS SCOPE_TABLE,
   NULL AS SOURCE_DATA_TYPE,
   'NO' AS IS_AUTOINCREMENT,
-  'NO' AS IS_GENERATEDCOLUMN
+  CASE
+    WHEN (IS_GENERATED = 'NEVER') THEN 'NO'
+    ELSE 'YES'
+  END AS IS_GENERATEDCOLUMN
 FROM INFORMATION_SCHEMA.COLUMNS C
 WHERE UPPER(C.TABLE_CATALOG) LIKE ?
   AND UPPER(C.TABLE_SCHEMA) LIKE ?

src/test/java/com/google/cloud/spanner/jdbc/it/ITJdbcDatabaseMetaDataTest.java

@@ -25,6 +25,7 @@
 
 import com.google.cloud.spanner.IntegrationTest;
 import com.google.cloud.spanner.jdbc.ITAbstractJdbcTest;
+import com.google.cloud.spanner.testing.EmulatorSpannerHelper;
 import java.sql.Connection;
 import java.sql.DatabaseMetaData;
 import java.sql.ResultSet;
@@ -53,7 +54,8 @@ public class ITJdbcDatabaseMetaDataTest extends ITAbstractJdbcTest {
 
   @BeforeClass
   public static void skipOnEmulator() {
-    assumeFalse("foreign keys are not supported on the emulator", env.getTestHelper().isEmulator());
+    assumeFalse(
+        "foreign keys are not supported on the emulator", EmulatorSpannerHelper.isUsingEmulator());
   }
 
   @Override
@@ -70,6 +72,7 @@ private static final class Column {
     private final Integer radix;
     private final boolean nullable;
     private final Integer charOctetLength;
+    private final boolean computed;
 
     private Column(
         String name,
@@ -80,6 +83,19 @@ private Column(
         Integer radix,
         boolean nullable,
         Integer charOctetLength) {
+      this(name, type, typeName, colSize, decimalDigits, radix, nullable, charOctetLength, false);
+    }
+
+    private Column(
+        String name,
+        int type,
+        String typeName,
+        Integer colSize,
+        Integer decimalDigits,
+        Integer radix,
+        boolean nullable,
+        Integer charOctetLength,
+        boolean computed) {
       this.name = name;
       this.type = type;
       this.typeName = typeName;
@@ -88,6 +104,7 @@ private Column(
       this.radix = radix;
       this.nullable = nullable;
       this.charOctetLength = charOctetLength;
+      this.computed = computed;
     }
   }
 
@@ -133,7 +150,17 @@ private Column(
           new Column("ColDateArray", Types.ARRAY, "ARRAY<DATE>", 10, null, null, true, null),
           new Column(
               "ColTimestampArray", Types.ARRAY, "ARRAY<TIMESTAMP>", 35, null, null, true, null),
-          new Column("ColNumericArray", Types.ARRAY, "ARRAY<NUMERIC>", 15, null, 10, true, null));
+          new Column("ColNumericArray", Types.ARRAY, "ARRAY<NUMERIC>", 15, null, 10, true, null),
+          new Column(
+              "ColComputed",
+              Types.NVARCHAR,
+              "STRING(MAX)",
+              2621440,
+              null,
+              null,
+              true,
+              2621440,
+              true));
 
   @Test
   public void testGetColumns() throws SQLException {
@@ -195,7 +222,7 @@ public void testGetColumns() throws SQLException {
           assertThat(rs.getShort("SOURCE_DATA_TYPE"), is(equalTo((short) 0)));
           assertThat(rs.wasNull(), is(true));
           assertThat(rs.getString("IS_AUTOINCREMENT"), is(equalTo("NO")));
-          assertThat(rs.getString("IS_GENERATEDCOLUMN"), is(equalTo("NO")));
+          assertThat(rs.getString("IS_GENERATEDCOLUMN"), is(equalTo(col.computed ? "YES" : "NO")));
           assertThat(rs.getMetaData().getColumnCount(), is(equalTo(24)));
 
           pos++;

src/test/resources/com/google/cloud/spanner/jdbc/it/CreateMusicTables.sql

@@ -84,7 +84,9 @@ CREATE TABLE TableWithAllColumnTypes (
   ColBytesMaxArray	ARRAY<BYTES(MAX)>,
   ColDateArray		ARRAY<DATE>,
   ColTimestampArray	ARRAY<TIMESTAMP>,
-  ColNumericArray	ARRAY<NUMERIC>
+  ColNumericArray	ARRAY<NUMERIC>,
+  
+  ColComputed STRING(MAX) AS (CONCAT(COALESCE(ColString, ''), ' ', COALESCE(ColStringMax, ''))) STORED,
 ) PRIMARY KEY (ColInt64)
 ;