refactor: Removing duplicated code to handle array values (#2143)

* refactor: Removing duplicated code to handle array values

The same deserialization logic for data types have been duplicated at multiple places which is prone to error.

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

* refactor: Using lazy computation for all the data types and adding docs

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

Author: gauravpurohit06

google-cloud-spanner/src/main/java/com/google/cloud/spanner/AbstractResultSet.java

@@ -67,7 +67,6 @@
 import java.util.concurrent.TimeUnit;
 import java.util.logging.Level;
 import java.util.logging.Logger;
-import java.util.stream.Collectors;
 import javax.annotation.Nullable;
 
 /** Implementation of {@link ResultSet}. */
@@ -547,88 +546,24 @@ private static Struct decodeStructValue(Type structType, ListValue structValue)
 
     static Object decodeArrayValue(Type elementType, ListValue listValue) {
       switch (elementType.getCode()) {
-        case BOOL:
-          // Use a view: element conversion is virtually free.
-          return Lists.transform(
-              listValue.getValuesList(),
-              input -> input.getKindCase() == KindCase.NULL_VALUE ? null : input.getBoolValue());
         case INT64:
           // For int64/float64 types, use custom containers.  These avoid wrapper object
           // creation for non-null arrays.
           return new Int64Array(listValue);
         case FLOAT64:
           return new Float64Array(listValue);
+        case BOOL:
         case NUMERIC:
-          {
-            // Materialize list: element conversion is expensive and should happen only once.
-            ArrayList<Object> list = new ArrayList<>(listValue.getValuesCount());
-            for (com.google.protobuf.Value value : listValue.getValuesList()) {
-              list.add(
-                  value.getKindCase() == KindCase.NULL_VALUE
-                      ? null
-                      : new BigDecimal(value.getStringValue()));
-            }
-            return list;
-          }
         case PG_NUMERIC:
         case STRING:
         case JSON:
         case PG_JSONB:
-          return listValue.getValuesList().stream()
-              .map(
-                  input ->
-                      input.getKindCase() == KindCase.NULL_VALUE ? null : input.getStringValue())
-              .collect(Collectors.toList());
         case BYTES:
-          {
-            // Materialize list: element conversion is expensive and should happen only once.
-            ArrayList<Object> list = new ArrayList<>(listValue.getValuesCount());
-            for (com.google.protobuf.Value value : listValue.getValuesList()) {
-              list.add(
-                  value.getKindCase() == KindCase.NULL_VALUE
-                      ? null
-                      : ByteArray.fromBase64(value.getStringValue()));
-            }
-            return list;
-          }
         case TIMESTAMP:
-          {
-            // Materialize list: element conversion is expensive and should happen only once.
-            ArrayList<Object> list = new ArrayList<>(listValue.getValuesCount());
-            for (com.google.protobuf.Value value : listValue.getValuesList()) {
-              list.add(
-                  value.getKindCase() == KindCase.NULL_VALUE
-                      ? null
-                      : Timestamp.parseTimestamp(value.getStringValue()));
-            }
-            return list;
-          }
         case DATE:
-          {
-            // Materialize list: element conversion is expensive and should happen only once.
-            ArrayList<Object> list = new ArrayList<>(listValue.getValuesCount());
-            for (com.google.protobuf.Value value : listValue.getValuesList()) {
-              list.add(
-                  value.getKindCase() == KindCase.NULL_VALUE
-                      ? null
-                      : Date.parseDate(value.getStringValue()));
-            }
-            return list;
-          }
-
         case STRUCT:
-          {
-            ArrayList<Struct> list = new ArrayList<>(listValue.getValuesCount());
-            for (com.google.protobuf.Value value : listValue.getValuesList()) {
-              if (value.getKindCase() == KindCase.NULL_VALUE) {
-                list.add(null);
-              } else {
-                ListValue structValue = value.getListValue();
-                list.add(decodeStructValue(elementType, structValue));
-              }
-            }
-            return list;
-          }
+          return Lists.transform(
+              listValue.getValuesList(), input -> decodeValue(elementType, input));
         default:
           throw new AssertionError("Unhandled type code: " + elementType.getCode());
       }

google-cloud-spanner/src/main/java/com/google/cloud/spanner/StructReader.java

@@ -178,10 +178,18 @@ default Value getValue(String columnName) {
    */
   boolean[] getBooleanArray(String columnName);
 
-  /** Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.bool())}. */
+  /**
+   * Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.bool())}. The
+   * list returned by this method is lazily constructed. Create a copy of it if you intend to access
+   * each element in the list multiple times.
+   */
   List<Boolean> getBooleanList(int columnIndex);
 
-  /** Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.bool())}. */
+  /**
+   * Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.bool())}. The
+   * list returned by this method is lazily constructed. Create a copy of it if you intend to access
+   * each element in the list multiple times.
+   */
   List<Boolean> getBooleanList(String columnName);
 
   /**
@@ -200,10 +208,18 @@ default Value getValue(String columnName) {
    */
   long[] getLongArray(String columnName);
 
-  /** Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.int64())}. */
+  /**
+   * Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.int64())}. The
+   * list returned by this method is lazily constructed. Create a copy of it if you intend to access
+   * each element in the list multiple times.
+   */
   List<Long> getLongList(int columnIndex);
 
-  /** Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.int64())}. */
+  /**
+   * Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.int64())}. The
+   * list returned by this method is lazily constructed. Create a copy of it if you intend to access
+   * each element in the list multiple times.
+   */
   List<Long> getLongList(String columnName);
 
   /**
@@ -223,84 +239,136 @@ default Value getValue(String columnName) {
   double[] getDoubleArray(String columnName);
 
   /**
-   * Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.float64())}.
+   * Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.float64())} The
+   * list returned by this method is lazily constructed. Create a copy of it if you intend to access
+   * each element in the list multiple times.
    */
   List<Double> getDoubleList(int columnIndex);
 
   /**
-   * Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.float64())}.
+   * Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.float64())} The
+   * list returned by this method is lazily constructed. Create a copy of it if you intend to access
+   * each element in the list multiple times.
    */
   List<Double> getDoubleList(String columnName);
 
   /**
-   * Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.numeric())}.
+   * Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.numeric())} The
+   * list returned by this method is lazily constructed. Create a copy of it if you intend to access
+   * each element in the list multiple times.
    */
   List<BigDecimal> getBigDecimalList(int columnIndex);
 
   /**
-   * Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.numeric())}.
+   * Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.numeric())} The
+   * list returned by this method is lazily constructed. Create a copy of it if you intend to access
+   * each element in the list multiple times.
    */
   List<BigDecimal> getBigDecimalList(String columnName);
 
-  /** Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.string())}. */
+  /**
+   * Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.string())}. The
+   * list returned by this method is lazily constructed. Create a copy of it if you intend to access
+   * each element in the list multiple times.
+   */
   List<String> getStringList(int columnIndex);
 
-  /** Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.string())}. */
+  /**
+   * Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.string())}. The
+   * list returned by this method is lazily constructed. Create a copy of it if you intend to access
+   * each element in the list multiple times.
+   */
   List<String> getStringList(String columnName);
 
-  /** Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.json())}. */
+  /**
+   * Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.json())}. The
+   * list returned by this method is lazily constructed. Create a copy of it if you intend to access
+   * each element in the list multiple times.
+   */
   default List<String> getJsonList(int columnIndex) {
     throw new UnsupportedOperationException("method should be overwritten");
   };
 
-  /** Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.json())}. */
+  /**
+   * Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.json())}. The
+   * list returned by this method is lazily constructed. Create a copy of it if you intend to access
+   * each element in the list multiple times.
+   */
   default List<String> getJsonList(String columnName) {
     throw new UnsupportedOperationException("method should be overwritten");
   };
 
   /**
-   * Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.pgJsonb())}.
+   * Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.pgJsonb())} The
+   * list returned by this method is lazily constructed. Create a copy of it if you intend to access
+   * each element in the list multiple times.
    */
   default List<String> getPgJsonbList(int columnIndex) {
     throw new UnsupportedOperationException("method should be overwritten");
   };
 
   /**
-   * Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.pgJsonb())}.
+   * Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.pgJsonb())} The
+   * list returned by this method is lazily constructed. Create a copy of it if you intend to access
+   * each element in the list multiple times.
    */
   default List<String> getPgJsonbList(String columnName) {
     throw new UnsupportedOperationException("method should be overwritten");
   };
 
-  /** Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.bytes())}. */
+  /**
+   * Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.bytes())}. The
+   * list returned by this method is lazily constructed. Create a copy of it if you intend to access
+   * each element in the list multiple times.
+   */
   List<ByteArray> getBytesList(int columnIndex);
 
-  /** Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.bytes())}. */
+  /**
+   * Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.bytes())}. The
+   * list returned by this method is lazily constructed. Create a copy of it if you intend to access
+   * each element in the list multiple times.
+   */
   List<ByteArray> getBytesList(String columnName);
 
   /**
-   * Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.timestamp())}.
+   * Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.timestamp())}
+   * The list returned by this method is lazily constructed. Create a copy of it if you intend to
+   * access each element in the list multiple times.
    */
   List<Timestamp> getTimestampList(int columnIndex);
 
   /**
-   * Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.timestamp())}.
+   * Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.timestamp())}
+   * The list returned by this method is lazily constructed. Create a copy of it if you intend to
+   * access each element in the list multiple times.
    */
   List<Timestamp> getTimestampList(String columnName);
 
-  /** Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.date())}. */
+  /**
+   * Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.date())}. The
+   * list returned by this method is lazily constructed. Create a copy of it if you intend to access
+   * each element in the list multiple times.
+   */
   List<Date> getDateList(int columnIndex);
 
-  /** Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.date())}. */
+  /**
+   * Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.date())}. The
+   * list returned by this method is lazily constructed. Create a copy of it if you intend to access
+   * each element in the list multiple times.
+   */
   List<Date> getDateList(String columnName);
 
   /**
-   * Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.struct(...))}.
+   * Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.struct(...))}
+   * The list returned by this method is lazily constructed. Create a copy of it if you intend to
+   * access each element in the list multiple times.
    */
   List<Struct> getStructList(int columnIndex);
 
   /**
-   * Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.struct(...))}.
+   * Returns the value of a non-{@code NULL} column with type {@code Type.array(Type.struct(...))}
+   * The list returned by this method is lazily constructed. Create a copy of it if you intend to
+   * access each element in the list multiple times.
    */
   List<Struct> getStructList(String columnName);
 }