vihangk1 commented on a change in pull request #1470:
URL: https://github.com/apache/hive/pull/1470#discussion_r504957647
##########
File path:
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/DatabaseProduct.java
##########
@@ -20,71 +20,666 @@
import java.sql.SQLException;
import java.sql.SQLTransactionRollbackException;
+import java.sql.Timestamp;
+import java.util.ArrayList;
+import java.util.EnumMap;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
-/** Database product infered via JDBC. */
-public enum DatabaseProduct {
- DERBY, MYSQL, POSTGRES, ORACLE, SQLSERVER, OTHER;
+import org.apache.hadoop.conf.Configurable;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.hive.metastore.api.MetaException;
+import org.apache.hadoop.hive.metastore.conf.MetastoreConf;
+import org.apache.hadoop.hive.metastore.conf.MetastoreConf.ConfVars;
+import org.apache.hadoop.util.ReflectionUtils;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import com.google.common.base.Preconditions;
+
+/** Database product inferred via JDBC. Encapsulates all SQL logic associated
with
+ * the database product.
+ * This class is a singleton, which is instantiated the first time
+ * method determineDatabaseProduct is invoked.
+ * Tests that need to create multiple instances can use the reset method
+ * */
+public class DatabaseProduct implements Configurable {
+ static final private Logger LOG =
LoggerFactory.getLogger(DatabaseProduct.class.getName());
+
+ private static enum DbType {DERBY, MYSQL, POSTGRES, ORACLE, SQLSERVER,
CUSTOM, UNDEFINED};
+ public DbType dbType;
+
+ // Singleton instance
+ private static DatabaseProduct theDatabaseProduct;
+
+ Configuration myConf;
+ /**
+ * Protected constructor for singleton class
+ * @param id
+ */
+ protected DatabaseProduct() {}
+
+ public static final String DERBY_NAME = "derby";
+ public static final String SQL_SERVER_NAME = "microsoft sql server";
+ public static final String MYSQL_NAME = "mysql";
+ public static final String POSTGRESQL_NAME = "postgresql";
+ public static final String ORACLE_NAME = "oracle";
+ public static final String UNDEFINED_NAME = "other";
+
/**
* Determine the database product type
* @param productName string to defer database connection
* @return database product type
*/
- public static DatabaseProduct determineDatabaseProduct(String productName)
throws SQLException {
- if (productName == null) {
- return OTHER;
+ public static DatabaseProduct determineDatabaseProduct(String productName,
Configuration c) {
+ DbType dbt;
+
+ if (theDatabaseProduct != null) {
+ Preconditions.checkState(theDatabaseProduct.dbType ==
getDbType(productName));
+ return theDatabaseProduct;
}
+
+ // This method may be invoked by concurrent connections
+ synchronized (DatabaseProduct.class) {
+
+ if (productName == null) {
+ productName = UNDEFINED_NAME;
+ }
+
+ dbt = getDbType(productName);
+
+ // Check for null again in case of race condition
+ if (theDatabaseProduct == null) {
+ final Configuration conf = c!= null ? c :
MetastoreConf.newMetastoreConf();
+ // Check if we are using an external database product
+ boolean isExternal = MetastoreConf.getBoolVar(conf,
ConfVars.USE_CUSTOM_RDBMS);
+
+ if (isExternal) {
+ // The DatabaseProduct will be created by instantiating an external
class via
+ // reflection. The external class can override any method in the
current class
+ String className = MetastoreConf.getVar(conf,
ConfVars.CUSTOM_RDBMS_CLASSNAME);
+
+ if (className != null) {
+ try {
+ theDatabaseProduct = (DatabaseProduct)
+ ReflectionUtils.newInstance(Class.forName(className), conf);
+
+ LOG.info(String.format("Using custom RDBMS %s. Overriding
DbType: %s", className, dbt));
+ dbt = DbType.CUSTOM;
+ }catch (Exception e) {
+ LOG.warn("Caught exception instantiating custom database
product. Reverting to " + dbt, e);
+ }
+ }
+ else {
+ LOG.warn("Unexpected: metastore.use.custom.database.product was
set, " +
+ "but metastore.custom.database.product.classname was not.
Reverting to " + dbt);
+ }
+ }
+
+ if (theDatabaseProduct == null) {
+ theDatabaseProduct = new DatabaseProduct();
Review comment:
line 91 is initializing a local variable dbt. I see that
theDatabaseProducte.dbType = dbt is executed outside synchronized block later
below. We should probably move it in the synchronized block.
##########
File path:
standalone-metastore/metastore-common/src/main/java/org/apache/hadoop/hive/metastore/conf/MetastoreConf.java
##########
@@ -1337,6 +1337,15 @@ public static ConfVars getMetaConf(String name) {
HIVE_TXN_STATS_ENABLED("hive.txn.stats.enabled", "hive.txn.stats.enabled",
true,
"Whether Hive supports transactional stats (accurate stats for
transactional tables)"),
+ // External RDBMS support
+ USE_CUSTOM_RDBMS("metastore.use.custom.database.product",
+ "hive.metastore.use.custom.database.product", false,
+ "Use an external RDBMS for the metastore"),
Review comment:
Sorry, may be should have been clearer. I meant adding the text "Use an
external RDBMS which is not in the list of natively supported databases (e.g.
Derby, Mysql, Oracle, Postgres, MSSQL), as defined by hive.metastore.db.type.
If this configuration is true, the metastore.custom.database.product.classname
must be set to a valid class name" as the fourth argument in the
USE_CUSTOM_RDBMS. IIRC this description is used to generate the template for
default hive-site.xml so that the description is present in the xml file itself.
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