NimzyMaina opened a new issue, #32509:
URL: https://github.com/apache/beam/issues/32509
### What happened?
The method used to check whether a table exists on spanner can in some
scenarios always return `false` as there is no ability to specify the
`table_catalog` and `table_schema`. In my case, these fields are always
populated in the `information_schema.tables` view.
The first time I run the application, it runs fine as it creates the
metadata table. The problem arrises when I restart the application & specify
the same metadata table. It tries to recreate the table but it already exists
resulting in a Spanner Exception.
```
Caused by: com.google.cloud.spanner.SpannerException: FAILED_PRECONDITION:
Operation with name
"projects/<project>/instances/<instance>/databases/<db>/operations/..." failed
with status = GrpcStatusCode{transportCode=FAILED_PRECONDITION} and message =
Duplicate name in schema: java_metadata_2.
```
[Link to tableExists
code](https://github.com/apache/beam/blob/75a463790d7912c475939f8c63d62ffba2002b0a/sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/spanner/changestreams/dao/PartitionMetadataDao.java#L82)
```java
/**
* Checks whether the metadata table already exists in the database.
*
* @return true if the table exists, false if the table does not exist.
*/
public boolean tableExists() {
final String checkTableExistsStmt =
"SELECT t.table_name FROM information_schema.tables AS t "
+ "WHERE t.table_catalog = '' AND "
+ "t.table_schema = '' AND "
+ "t.table_name = '"
+ metadataTableName
+ "'";
try (ResultSet queryResultSet =
databaseClient
.singleUseReadOnlyTransaction()
.executeQuery(Statement.of(checkTableExistsStmt))) {
return queryResultSet.next();
}
}
```
[Link to Where it is
used](https://github.com/apache/beam/blob/75a463790d7912c475939f8c63d62ffba2002b0a/sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/spanner/changestreams/dofn/InitializeDoFn.java#L66)
```java
@ProcessElement
public void processElement(OutputReceiver<PartitionMetadata> receiver) {
PartitionMetadataDao partitionMetadataDao =
daoFactory.getPartitionMetadataDao();
if (!partitionMetadataDao.tableExists()) { // <-- Fails at this point on
restart
daoFactory.getPartitionMetadataAdminDao().createPartitionMetadataTable();
createFakeParentPartition();
}
final PartitionMetadata initialPartition =
Optional.ofNullable(partitionMetadataDao.getPartition(InitialPartition.PARTITION_TOKEN))
.map(mapperFactory.partitionMetadataMapper()::from)
.orElseThrow(
() -> new IllegalStateException("Initial partition not found
in metadata table."));
receiver.output(initialPartition);
}
```
This results in a scenario where a change stream consumer **cannot recover**
from a restart.
## Suggested solution
```java
/**
* Checks whether the metadata table already exists in the database.
*
* @return true if the table exists, false if the table does not exist.
*/
public boolean tableExists() {
final String checkTableExistsStmt =
"SELECT t.table_name FROM information_schema.tables AS t "
+ "WHERE t.table_name = '" + metadataTableName + "'";
try (ResultSet queryResultSet =
databaseClient
.singleUseReadOnlyTransaction()
.executeQuery(Statement.of(checkTableExistsStmt))) {
return queryResultSet.next();
}
}
```
### Issue Priority
Priority: 1 (data loss / total loss of function)
### Issue Components
- [ ] Component: Python SDK
- [X] Component: Java SDK
- [ ] Component: Go SDK
- [ ] Component: Typescript SDK
- [X] Component: IO connector
- [ ] Component: Beam YAML
- [ ] Component: Beam examples
- [ ] Component: Beam playground
- [ ] Component: Beam katas
- [ ] Component: Website
- [ ] Component: Infrastructure
- [ ] Component: Spark Runner
- [ ] Component: Flink Runner
- [ ] Component: Samza Runner
- [ ] Component: Twister2 Runner
- [ ] Component: Hazelcast Jet Runner
- [ ] Component: Google Cloud Dataflow Runner
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