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https://issues.apache.org/jira/browse/PHOENIX-476?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15497545#comment-15497545
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Kevin Liew commented on PHOENIX-476:
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The SQL92 spec states:
{noformat}
4) Let Q be the result of that <query expression>.
Case:
a) If Q is empty, then no row is inserted and a completion con-
dition is raised: no data.
b) Otherwise, for each row R of Q:
i) A candidate row of B is effectively created in which the
value of each column is its default value, as specified in
the General Rules of Subclause 11.5, "<default clause>".
The candidate row includes every column of B.
ii) For every object column in the candidate row, the value of
the object column identified by the i-th <column name> in
the <insert column list> is replaced by the i-th value of
R.
iii) Let C be a column that is represented in the candidate row
and let SV be its value in the candidate row. The General
Rules of Subclause 9.2, "Store assignment", are applied to
C and SV as TARGET and VALUE, respectively.
iv) The candidate row is inserted into B.
Note: The data values allowable in the candidate row may be
constrained by a WITH CHECK OPTION constraint. The effect
of a WITH CHECK OPTION constraint is defined in the General
Rules of Subclause 11.19, "<view definition>".
{noformat}
In step `b.i`, a candidate row with all default values will be constructed.
Step `b.ii` is a bit ambiguous but I'd interpret that step such that a default
value value could be overwritten with a null value.
I tested with MySQL and Postgres and they both allow overwriting a default with
a null value. Any input [~julianhyde]?
> 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.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.
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