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https://issues.apache.org/jira/browse/PHOENIX-476?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15556975#comment-15556975
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James Taylor commented on PHOENIX-476:
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Thanks for the update, but I really need to see an updated patch at this point,
[~kliew] to further advise you. The persistence is handled already - all you
have to do is set the ColumnDef.expressionStr member variable. You can get the
string version of a ParseNode using the {{parseNode.toString()}} method. This
is what you need to set the expressionStr member variable to. Please make sure
your patch covers these feedback items I already gave you:
- Instead of using ExpressionUtil.isConstant(), use the following check:
{code}
expression.isStateless() && expression.getDeterminism() == Determinism.ALWAYS
{code}
- Don't wrap RowKeyExpression with getDefaultExpression for columns in the row
key as we need to store the row key with the default value. To do this, change
this code you added in ExpressionCompiler:
{code}
+ if (column.getDefaultExpression() != null &&
!SchemaUtil.isPKColumn(column)) {
+ expression = new DefaultValueExpression(Arrays.asList(expression,
column.getDefaultExpression()));
+ }
{code}
- Instead of ptr.copyBytes(), use ByteUtil.copyKeyBytesIfNecessary(ptr) as that
prevents a copy when it's not necessary.
- See https://phoenix.apache.org/building_website.html for how to update the
website
> 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.
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