moulimukherjee commented on a change in pull request #416: Adding docs on how
to use custom catalog with iceberg
URL: https://github.com/apache/incubator-iceberg/pull/416#discussion_r318291645
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File path: site/docs/custom-catalog.md
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@@ -0,0 +1,149 @@
+# Custom Catalog Implementation
+
+It's possible to read an iceberg table either from an hdfs path or from a hive
table. It's also possible to use a custom metastore in place of hive. The steps
to do that are as follows.
+
+- [Custom TableOperations](#custom-table-operations-implementation)
+- [Custom Catalog](#custom-table-implementation)
+- [Custom IcebergSource](#custom-icebergsource)
+
+### Custom table operations implementation
+Extend `BaseMetastoreTableOperations` to provide implementation on how to read
and write metadata
+
+Example:
+```java
+class CustomTableOperations extends BaseMetastoreTableOperations {
+ private String dbName;
+ private String tableName;
+ private Configuration conf;
+ private FileIO fileIO;
+
+ protected CustomTableOperations(Configuration conf, String dbName, String
tableName) {
+ this.conf = conf;
+ this.dbName = dbName;
+ this.tableName = tableName;
+ }
+
+ // The doRefresh method should provide implementation on how to get the
metadata location
+ @Override
+ public void doRefresh() {
+
+ // Example custom service which returns the metadata location given a
dbName and tableName
+ String metadataLocation = CustomService.getMetadataForTable(conf, dbName,
tableName);
+
+ // Use existing method to refresh metadata
+ refreshFromMetadataLocation(metadataLocation);
+
+ }
+
+ // The doCommit method should provide implementation on how to update with
metadata location atomically
+ @Override
+ public void doCommit(TableMetadata base, TableMetadata metadata) {
+ // if the metadata is already out of date, reject it
+ if (base != current()) {
Review comment:
Added it at https://github.com/apache/incubator-iceberg/pull/419, will
remove it from here.
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