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From "James Taylor (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (PHOENIX-3823) Force cache update on MetaDataEntityNotFoundException
Date Fri, 05 May 2017 19:49:05 GMT

    [ https://issues.apache.org/jira/browse/PHOENIX-3823?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15998867#comment-15998867
] 

James Taylor commented on PHOENIX-3823:
---------------------------------------

One thought I had (which I meant to share with you earlier) is that we should do the same
retry logic for create table call in PhoenixStatement. We can perhaps put your retry logic
in this one place to cover all cases:
{code}
    protected boolean execute(final CompilableStatement stmt) throws SQLException {
{code}

Sounds like there may be an additional problem here too, in particular with view creation.
There's some special logic in CreateTableStatement that freezes the timestamp at the one on
the tableRef+1 that likely needs to be changed here:
{code}
                if (viewTypeToBe != ViewType.MAPPED) {
                    Long scn = connection.getSCN();
                    connectionToBe = (scn != null || tableRef.getTable().isTransactional())
? connection :
                        // If we haved no SCN on our connection and the base table is not
transactional, freeze the SCN at when
                        // the base table was resolved to prevent any race condition on
                        // the error checking we do for the base table. The only potential
                        // issue is if the base table lives on a different region server
                        // than the new table will, then we're relying here on the system
                        // clocks being in sync.
                        new PhoenixConnection(
                            // When the new table is created, we still want to cache it
                            // on our connection.
                            new DelegateConnectionQueryServices(connection.getQueryServices())
{
                                @Override
                                public void addTable(PTable table, long resolvedTime) throws
SQLException {
                                    connection.addTable(table, resolvedTime);
                                }
                            },
                            connection, tableRef.getTimeStamp()+1);
{code}


> Force cache update on MetaDataEntityNotFoundException 
> ------------------------------------------------------
>
>                 Key: PHOENIX-3823
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-3823
>             Project: Phoenix
>          Issue Type: Sub-task
>            Reporter: James Taylor
>            Assignee: Maddineni Sukumar
>
> When UPDATE_CACHE_FREQUENCY is used, clients will cache metadata for a period of time
which may cause the schema being used to become stale. If another client adds a column or
a new table or view, other clients won't see it. As a result, the client will get a MetaDataEntityNotFoundException.
Instead of bubbling this up, we should retry after forcing a cache update on the tables involved
in the query.
> The above works well for references to entities that don't yet exist. However, we cannot
detect when some entities are referred to which no longer exists until the cache expires.
An exception is if a physical table is dropped which would be detected immediately, however
we would allow queries and updates to columns which have been dropped until the cache entry
expires (which seems like a reasonable tradeoff IMHO. In addition, we won't start using indexes
on tables until the cache expires.



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