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https://issues.apache.org/jira/browse/DERBY-118?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13288920#comment-13288920
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Dag H. Wanvik edited comment on DERBY-118 at 6/4/12 9:35 PM:
-------------------------------------------------------------
As for type checking, conversion and code sharing, I think we are ok:
InsertNode#bindStatement:
checks the type compatibility here:
a)
resultColumnList.checkStorableExpressions(resultSet.getResultColumns());
which mobilizes TypeCompilers (ca line 461)
ResultColumn#checkStorableExpression:
:
if (!getTypeCompiler().storable(toStoreTypeId, getClassFactory())) {
throw..
which in turn calls
NumericTypeCompiler#numberStorable
and a decimal passes muster for an int column, for example:
:
if (otherType.isNumericTypeId()) { return true; }
then later in bindStatement, ca line 470
b) NormalizeResultSetNode#init - see class Javadoc example for storing
"2.0" into a BIGINT.
inserts a node to actually convert the value to the type of
the column, e.g leads to the correct code generation for
it, possibly throwing for truncation etc.
ColumnDefinitionNode:
after the special checks for default, also uses the type
compiler to check, cf.
ColumnDefinitionNode#validateDefault:
:
// Now check 'not storable' errors.
if (! getTypeCompiler(columnTypeId).
storable(defaultTypeId, getClassFactory())) {
throw..
If this passes, the conversion will be handled the same way as
in plain insert, since, the default value is expanded *before*
the NormalizeResultSetNode of InertNode#bindStatement is
constructed:
InsertNode#bindStatement, ca line 323
:
/* Replace any DEFAULTs with the associated tree, or flag DEFAULTs if
* not allowed (inside top level set operator nodes). Subqueries are
* checked for illegal DEFAULTs elsewhere.
*/
resultSet.replaceOrForbidDefaults(targetTableDescriptor,
targetColumnList,
isTableConstructor);
so, my conclusion is the conversion code is shared here. No cast node
is needed either.
was (Author: dagw):
As for type checking, conversion and code sharing, I think we are ok:
InsertNode#bindStatement:
checks the type compatibility here:
a)
resultColumnList.checkStorableExpressions(resultSet.getResultColumns());
which mobilizes TypeCompilers (ca line 461)
ResultColumn#checkStorableExpression:
:
if (!getTypeCompiler().storable(toStoreTypeId, getClassFactory())) {
throw..
which in turn calls
NumericTypeCompiler#numberStorable
and a decimal passes muster:
:
if (otherType.isNumericTypeId()) { return true; }
then later in bindStatement, ca line 470
b) NormalizeResultSetNode#init - see class Javadoc example for storing
"2.0" into a BIGINT.
inserts a node to actually convert the value to the type of
the column, e.g leads to the correct code generation for
it, possibly throwing for truncation etc.
ColumnDefinitionNode:
after the special checks for default, also uses the type
compiler to check, cf.
ColumnDefinitionNode#validateDefault:
:
// Now check 'not storable' errors.
if (! getTypeCompiler(columnTypeId).
storable(defaultTypeId, getClassFactory())) {
throw..
If this passes, the conversion will be handled the same way as
in plain insert, since, the default value is expanded *before*
the NormalizeResultSetNode of InertNode#bindStatement is
constructed:
InsertNode#bindStatement, ca line 323
:
/* Replace any DEFAULTs with the associated tree, or flag DEFAULTs if
* not allowed (inside top level set operator nodes). Subqueries are
* checked for illegal DEFAULTs elsewhere.
*/
resultSet.replaceOrForbidDefaults(targetTableDescriptor,
targetColumnList,
isTableConstructor);
so, my conclusion is the conversion code is shared here. No cast node
is needed either.
> Lift some DB2 restrictions on DEFAULT values [was: Allow any build-in
> function as default values in table create for columns]
> -----------------------------------------------------------------------------------------------------------------------------
>
> Key: DERBY-118
> URL: https://issues.apache.org/jira/browse/DERBY-118
> Project: Derby
> Issue Type: Improvement
> Components: SQL
> Reporter: Bernd Ruehlicke
> Assignee: Dag H. Wanvik
> Priority: Minor
> Attachments: derby-118-all-defaults.diff, derby-118-longvarchar.diff,
> derby-118.diff, derby-118.stat, derby-118b.diff, derby-118b.stat,
> derby-118c.diff, derby-118c.stat
>
>
> It is ok in ij to do a values char(current_date) but is is not allowed to
> use char(current_date) as default value for clolumns; like for example
> CREATE TABLE DOSENOTWORK (num int, created_by varchar(40) default user,
> create_date_string varchar(40) default char(current_date))
> Request: It should be allowed to use any build-in function which return a
> valid type as part of the default value spec.
> There was a e-mail thread for this and the core content/answer was:
> Bernd Ruehlicke wrote:
> >
> > CREATE TABLE DOSENOTWORK (num int, created_by varchar(40) default
> > user, create_date_string varchar(40) default char(current_date))
> >
> > give an error as below - any idea why ?!??!
> >
> The rules for what is acceptable as a column default in Derby say that the
> only valid functions are datetime functions.
> The logic that enforces this can be seen in the "defaultTypeIsValid" method
> of the file:
> ./java/engine/org/apache/derby/impl/sql/compile/ColumnDefinitionNode.java
> The Derby Reference Manual also states this same restriction (albeit rather
> briefly):
> ----
> Column Default
> For the definition of a default value, a ConstantExpression is an expression
> that does not refer to any table. It can include constants, date-time special
> registers, current schemas, users, and null.
> ----
> A "date-time special register" here means a date-time function such as
> "date(current_date)" in your first example.
> Since the function "char" is NOT a date-time function, it will throw an error.
> I believe this restriction was put in place as part of the "DB2
> compatibility" work was that done in Cloudscape a while back.
> Hope that answers your question,
> Army
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