Added a migrating guide

Bigtable/MIGRATING.md

@@ -0,0 +1,66 @@
+# Migrating Google Cloud Bigtable from V1 to V2
+
+## How to upgrade
+
+Update your `google/cloud-bigtable` dependency to `^2.0`:
+
+```
+{
+    "require": {
+        "google/cloud-bigtable": "^2.0"
+    }
+}
+```
+
+## Changes
+
+### Retry Options changes
+
+The `retries` parameter in the following RPC calls is changed to `retrySettings.maxRetries`:
+- Google\Cloud\Bigtable\Table::mutateRows
+- Google\Cloud\Bigtable\Table::upsert
+- Google\Cloud\Bigtable\Table::readRows
+
+For example:
+```php
+$table->readRows([
+    'retrySettings' => [
+        'maxRetries' => 3
+    ]
+]);
+```
+
+OR
+
+```php
+$retrySettings = RetrySettings::constructDefault();
+$retrySettings = $retrySettings->with(['maxRetries' => 3])
+$table->readRows([
+    'retrySettings' => $retrySettings
+]);
+```
+
+This is done in order to be consistent across other RPC calls which use GAX's retrySettings and to be consistent across other products which mostly use the [RetrySettings](https://github.com/googleapis/gax-php/blob/main/src/RetrySettings.php) from GAX already.
+
+Only the maxRetries parameter is supported for now and not the other options in the `RetrySettings`.
+
+### Removed deprecated classes
+
+The following deprecated classes are now removed completely. Use the specified alternatives.
+- `Google\Cloud\Bigtable\V2\MutateRowsRequest_Entry`, use `Google\Cloud\Bigtable\V2\MutateRowsRequest\Entry` instead.
+- `Google\Cloud\Bigtable\V2\MutateRowsResponse_Entry`, use `Google\Cloud\Bigtable\V2\MutateRowsResponse\Entry` instead.
+- `Google\Cloud\Bigtable\V2\Mutation_DeleteFromFamily`, use `Google\Cloud\Bigtable\V2\Mutation\DeleteFromFamily` instead.
+- `Google\Cloud\Bigtable\V2\Mutation_DeleteFromColumn`, use `Google\Cloud\Bigtable\V2\Mutation\DeleteFromColumn` instead.
+- `Google\Cloud\Bigtable\V2\Mutation_DeleteFromRow`, use `Google\Cloud\Bigtable\V2\Mutation\DeleteFromRow` instead.
+- `Google\Cloud\Bigtable\V2\Mutation_SetCell`, use `Google\Cloud\Bigtable\V2\Mutation\SetCell` instead.
+- `Google\Cloud\Bigtable\V2\ReadChangeStreamResponse_CloseStream`, use Google\Cloud\Bigtable\V2\ReadChangeStreamResponse\CloseStream`` instead.
+- `Google\Cloud\Bigtable\V2\ReadChangeStreamResponse_DataChange_Type`, use `Google\Cloud\Bigtable\V2\ReadChangeStreamResponse\DataChange\Type` instead.
+- `Google\Cloud\Bigtable\V2\ReadChangeStreamResponse_DataChange`, use `Google\Cloud\Bigtable\V2\ReadChangeStreamResponse\DataChange` instead.
+- `Google\Cloud\Bigtable\V2\ReadChangeStreamResponse_Heartbeat`, use `Google\Cloud\Bigtable\V2\ReadChangeStreamResponse\Heartbeat` instead.
+- `Google\Cloud\Bigtable\V2\ReadChangeStreamResponse_MutationChunk_ChunkInfo`, use `Google\Cloud\Bigtable\V2\ReadChangeStreamResponse\MutationChunk\ChunkInfo` instead.
+- `Google\Cloud\Bigtable\V2\ReadChangeStreamResponse_MutationChunk`, use `Google\Cloud\Bigtable\V2\ReadChangeStreamResponse\MutationChunk` instead.
+- `Google\Cloud\Bigtable\V2\ReadRowsRequest_RequestStatsView`, use `Google\Cloud\Bigtable\V2\ReadRowsRequest\RequestStatsView` instead.
+- `Google\Cloud\Bigtable\V2\RowFilter_Chain`, use `Google\Cloud\Bigtable\V2\RowFilter\Chain` instead.
+- `Google\Cloud\Bigtable\V2\RowFilter_Condition`, use `Google\Cloud\Bigtable\V2\RowFilter\Condition` instead.
+- `Google\Cloud\Bigtable\V2\RowFilter_Interleave`, use `Google\Cloud\Bigtable\V2\RowFilter\Interleave` instead.
+- `Google\Cloud\Bigtable\V2\ReadRowsResponse_CellChunk`, use `Google\Cloud\Bigtable\V2\ReadRowsResponse\CellChunk` instead.

Bigtable/README.md

@@ -66,6 +66,8 @@ foreach ($rows as $row) {
 This component is considered GA (generally available). As such, it will not introduce backwards-incompatible changes in
 any minor or patch releases. We will address issues and requests with the highest priority.
 
+Please see the [migration guide](./MIGRATING.md) to upgrade from **V1** of the library to **V2**.
+
 ### Next Steps
 
 Take a look at and understand the [official documentation](https://cloud.google.com/bigtable/docs).