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https://issues.apache.org/jira/browse/HIVE-675?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12753396#action_12753396
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He Yongqiang commented on HIVE-675:
-----------------------------------
>>Assuming Hive is an inner field of SessionState, we don't need to protect the
>>current database with another level of ThreadLocal.
yes. hive is a singleton object.
{noformat}
public class Hive {
static final private Log LOG = LogFactory.getLog("hive.ql.metadata.Hive");
static Hive db = null;
.........
public static Hive get(HiveConf c, boolean needsRefresh) throws HiveException
{
if(db == null || needsRefresh) {
closeCurrent();
c.set("fs.scheme.class","dfs");
db = new Hive(c);
}
return db;
}
{noformat}
So even though Hive is an inner field of SessionState, but i think they all
refer to the singleton instance at runtime. So we need to make the current
database be a ThreadLocal variable.
> add database/scheme support Hive QL
> -----------------------------------
>
> Key: HIVE-675
> URL: https://issues.apache.org/jira/browse/HIVE-675
> Project: Hadoop Hive
> Issue Type: New Feature
> Components: Query Processor
> Reporter: Prasad Chakka
> Assignee: He Yongqiang
> Attachments: hive-675-2009-9-7.patch, hive-675-2009-9-8.patch
>
>
> Currently all Hive tables reside in single namespace (default). Hive should
> support multiple namespaces (databases or schemas) such that users can create
> tables in their specific namespaces. These name spaces can have different
> warehouse directories (with a default naming scheme) and possibly different
> properties.
> There is already some support for this in metastore but Hive query parser
> should have this feature as well.
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