Implement schemaExists for Hive

Same logic as implemented in Iceberg. This should make certain operations faster.
trinodb · Sep 2, 2023 · 9d95bff · 9d95bff
1 parent 1b2b8c0
commit 9d95bff
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Showing 2 changed files with 17 additions and 3 deletions.
diff --git a/plugin/trino-hive/src/main/java/io/trino/plugin/hive/HiveMetadata.java b/plugin/trino-hive/src/main/java/io/trino/plugin/hive/HiveMetadata.java
@@ -318,6 +318,7 @@
 import static io.trino.spi.type.VarcharType.createUnboundedVarcharType;
 import static java.lang.Boolean.parseBoolean;
 import static java.lang.String.format;
+import static java.util.Locale.ENGLISH;
 import static java.util.Objects.requireNonNull;
 import static java.util.function.Function.identity;
 import static java.util.stream.Collectors.joining;
@@ -460,6 +461,20 @@ public DirectoryLister getDirectoryLister()
         return directoryLister;
     }
 
+    @Override
+    public boolean schemaExists(ConnectorSession session, String schemaName)
+    {
+        if (!schemaName.equals(schemaName.toLowerCase(ENGLISH))) {
+            // Currently, Trino schemas are always lowercase, so this one cannot exist (https://github.com/trinodb/trino/issues/17)
+            // In fact, some metastores (e.g. Glue) store database names lowercase only, but accepted mixed case on lookup, so we need to filter out here.
+            return false;
+        }
+        if (isHiveSystemSchema(schemaName)) {
+            return false;
+        }
+        return metastore.getDatabase(schemaName).isPresent();
+    }
+
     @Override
     public List<String> listSchemaNames(ConnectorSession session)
     {

diff --git a/...rc/test/java/io/trino/plugin/hive/metastore/thrift/TestHiveMetastoreAccessOperations.java b/...rc/test/java/io/trino/plugin/hive/metastore/thrift/TestHiveMetastoreAccessOperations.java
@@ -29,7 +29,6 @@
 import java.io.File;
 
 import static io.trino.plugin.hive.metastore.CountingAccessHiveMetastore.Method.CREATE_TABLE;
-import static io.trino.plugin.hive.metastore.CountingAccessHiveMetastore.Method.GET_ALL_DATABASES;
 import static io.trino.plugin.hive.metastore.CountingAccessHiveMetastore.Method.GET_DATABASE;
 import static io.trino.plugin.hive.metastore.CountingAccessHiveMetastore.Method.GET_PARTITIONS_BY_NAMES;
 import static io.trino.plugin.hive.metastore.CountingAccessHiveMetastore.Method.GET_PARTITION_NAMES_BY_FILTER;
@@ -73,7 +72,7 @@ public void testUse()
     {
         assertMetastoreInvocations("USE " + getSession().getSchema().orElseThrow(),
                 ImmutableMultiset.builder()
-                        .add(GET_ALL_DATABASES)
+                        .add(GET_DATABASE)
                         .build());
     }
 
@@ -220,7 +219,7 @@ public void testDescribe()
 
         assertMetastoreInvocations("DESCRIBE test_describe",
                 ImmutableMultiset.builder()
-                        .add(GET_ALL_DATABASES)
+                        .add(GET_DATABASE)
                         .add(GET_TABLE)
                         .build());
     }