Kevin Liew updated PHOENIX-476:
    Attachment: PHOENIX-476.3.patch

I attached a new patch implementing default values for both primary and 
row-value columns. 

There are a few issues though.

* After compiling a default value ParseNode into an Expression, it becomes a 
LiteralExpression. For `CURRENT_DATE()`, the ParseNode is stateless and the 
compiled `Expression.isConstant` is true so we aren’t able to throw an 
exception. Is there a existing expression compiler or a flag that will not 
convert the default value ParseNode to LiteralExpression?
Setting `requiresFinalEvaluation` did not change the result.

* DefaultValueExpression wraps a ProjectedColumnExpression in 
I modified `ProjectedColumnExpression.evaluate`  so that it returns true if the 
cell contains a null value.
But `KeyValueSchema.next` returns `null` for trailing nulls in a row 
`ProjectedColumnExpression.evaluate` cannot differentiate between a trailing 
null and trailing default value.
If we change the return value contract of `KeyValueSchema.next`, it causes 
failures in other test cases (ie. SortMergeIT).
I’m not familiar with the serialization scheme for rows returned by the region 
servers, but I suspect that trailing nulls are trimmed, which might be why 
`KeyValueSchema.next` does not account for trailing nulls.

The following test case (which isn't in the patch) fails due to a trailing 
default value that is overwritten by a null value:

    public void testCreateTableTrailingNullOverwritingDefault() throws 
Exception {
        String table = generateRandomString();
        String ddl = "CREATE TABLE " + table + " (" +
                "pk INTEGER PRIMARY KEY, " +
                "def INTEGER DEFAULT 1 + 9)";

        long ts = nextTimestamp();
        Properties props = new Properties();
        props.setProperty(PhoenixRuntime.CURRENT_SCN_ATTRIB, Long.toString(ts));
        Connection conn = DriverManager.getConnection(getUrl(), props);

        String dml = "UPSERT INTO " + table + " VALUES (1, null)";

        props.setProperty(PhoenixRuntime.CURRENT_SCN_ATTRIB, Long.toString(ts + 
        conn = DriverManager.getConnection(getUrl(), props);

        ResultSet rs = conn.createStatement().executeQuery("SELECT * FROM " + 
table + " WHERE pk = 1");
        assertEquals(1, rs.getInt(1));
        assertEquals(0, rs.getInt(2));

> Support declaration of DEFAULT in CREATE statement
> --------------------------------------------------
>                 Key: PHOENIX-476
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-476
>             Project: Phoenix
>          Issue Type: Task
>    Affects Versions: 3.0-Release
>            Reporter: James Taylor
>            Assignee: Kevin Liew
>              Labels: enhancement
>         Attachments: PHOENIX-476.2.patch, PHOENIX-476.3.patch, 
> PHOENIX-476.patch
> Support the declaration of a default value in the CREATE TABLE/VIEW statement 
> like this:
>     CREATE TABLE Persons (
>         Pid int NOT NULL PRIMARY KEY,
>         LastName varchar(255) NOT NULL,
>         FirstName varchar(255),
>         Address varchar(255),
>         City varchar(255) DEFAULT 'Sandnes'
>     )
> To implement this, we'd need to:
> 1. add a new DEFAULT_VALUE key value column in SYSTEM.TABLE and pass through 
> the value when the table is created (in MetaDataClient).
> 2. always set NULLABLE to ResultSetMetaData.columnNoNulls if a default value 
> is present, since the column will never be null.
> 3. add a getDefaultValue() accessor in PColumn
> 4.  for a row key column, during UPSERT use the default value if no value was 
> specified for that column. This could be done in the PTableImpl.newKey method.
> 5.  for a key value column with a default value, we can get away without 
> incurring any storage cost. Although a little bit of extra effort than if we 
> persisted the default value on an UPSERT for key value columns, this approach 
> has the benefit of not incurring any storage cost for a default value.
>     * serialize any default value into KeyValueColumnExpression
>     * in the evaluate method of KeyValueColumnExpression, conditionally use 
> the default value if the column value is not present. If doing partial 
> evaluation, you should not yet return the default value, as we may not have 
> encountered the the KeyValue for the column yet (since a filter evaluates 
> each time it sees each KeyValue, and there may be more than one KeyValue 
> referenced in the expression). Partial evaluation is determined by calling 
> Tuple.isImmutable(), where false means it is NOT doing partial evaluation, 
> while true means it is.
>     * modify EvaluateOnCompletionVisitor by adding a visitor method for 
> RowKeyColumnExpression and KeyValueColumnExpression to set 
> evaluateOnCompletion to true if they have a default value specified. This 
> will cause filter evaluation to execute one final time after all KeyValues 
> for a row have been seen, since it's at this time we know we should use the 
> default value.

This message was sent by Atlassian JIRA

Reply via email to