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https://issues.apache.org/jira/browse/PHOENIX-476?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15598225#comment-15598225
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James Taylor edited comment on PHOENIX-476 at 10/22/16 5:53 PM:
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No parser changes are required:
- In CreateTableCompiler, when you compile the defaultExpression, you'll end up
with a LiteralExpression (i.e. DEFAULT -2 + 7 would be turned into a
LiteralExpression of 5). Create a new CreateTableStatement copy constructor
that passes in a createTableStatement and an expressionStr. Use this to create
a new CreateTableStatement using defaultExpression.toString() to form the
literal expression string which you'll pass through to the MetaDataClient to
guarantee that the default expression is always a literal.
- By evaluating the default expression at CREATE TABLE time, and storing the
evaluated expression string value, you'll know you have literal. When reading
and parsing the default value back in PTableImpl, you can assume it's already a
literal and parse it as you were doing in your previous patch:
{code}
+ LiteralParseNode defaultParseNode = new
SQLParser(column.getExpressionStr()).parseLiteral();
+ LiteralExpression defaultLiteral =
LiteralExpression.newConstant(defaultParseNode.getValue(),
column.getDataType(), column.getMaxLength(), column.getScale(),
column.getSortOrder(), Determinism.ALWAYS);
+ ImmutableBytesWritable valuePtr = new
ImmutableBytesWritable();
+ defaultLiteral.evaluate(null, valuePtr);
+ byteValue =
ByteUtil.copyKeyBytesIfNecessary(valuePtr);
{code}
was (Author: jamestaylor):
No parser changes are required:
-In CreateTableCompiler, when you compile the defaultExpression, you'll end up
with a LiteralExpression (i.e. DEFAULT -2 + 7 would be turned into a
LiteralExpression of 5). Create a new CreateTableStatement copy constructor
that passes in a createTableStatement and an expressionStr. Use this to create
a new CreateTableStatement using defaultExpression.toString() to form the
literal expression string which you'll pass through to the MetaDataClient to
guarantee that the default expression is always a literal.
- By evaluating the default expression at CREATE TABLE time, and storing the
evaluated expression string value, you'll know you have literal. When reading
and parsing the default value back in PTableImpl, you can assume it's already a
literal and parse it as you were doing in your previous patch:
{code}
+ LiteralParseNode defaultParseNode = new
SQLParser(column.getExpressionStr()).parseLiteral();
+ LiteralExpression defaultLiteral =
LiteralExpression.newConstant(defaultParseNode.getValue(),
column.getDataType(), column.getMaxLength(), column.getScale(),
column.getSortOrder(), Determinism.ALWAYS);
+ ImmutableBytesWritable valuePtr = new
ImmutableBytesWritable();
+ defaultLiteral.evaluate(null, valuePtr);
+ byteValue =
ByteUtil.copyKeyBytesIfNecessary(valuePtr);
{code}
> 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
> Fix For: 4.9.0
>
> Attachments: PHOENIX-476.2.patch, PHOENIX-476.3.patch,
> PHOENIX-476.4.patch, PHOENIX-476.5.patch, PHOENIX-476.6.patch,
> PHOENIX-476.7.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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