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https://issues.apache.org/jira/browse/DERBY-532?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13930339#comment-13930339
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Dag H. Wanvik edited comment on DERBY-532 at 3/11/14 2:09 PM:
--------------------------------------------------------------
That's correct. That directive is what I use to make Derby use the non-standard
scan when we check the violations when the constraint mode changes back to
immediate. Cf. this code in DeferredConstraintsMemory#validateCheck, ca. line
476:
{code}
// If a compress has happened in this transaction, we can't
// trust the rowLocations, so make a full table scan. If
// not, we optimize by using a special result set type
// which utilized the saved away row locations for the
// offending rows, so we only visit those when checking.
// I.e. other rows are known to be good a priori.
if (!ci.isInvalidated()) {
checkStmt.append(
" --DERBY-PROPERTIES joinStrategy=nestedLoop, " +
" index=null, " +
" validateCheckConstraint=");
checkStmt.append(Long.toString(baseTableCID));
checkStmt.append('\n');
}
checkStmt.append(" WHERE NOT(");
checkStmt.append(cd.getConstraintText());
checkStmt.append(')');
{code}
This is normal code path, though, not only for debugging.
was (Author: dagw):
That's correct. That directive is what I use to make Derby use the non-standard
scan when we check the violations when the constraint mode changes back to
immediate. Cf. this code in DeferredConstraintsMemory#validateCheck, ca. line
476:
{code}
// If a compress has happened in this transaction, we can't
// trust the rowLocations, so make a full table scan. If
// not, we optimize by using a special result set type
// which utilized the saved away row locations for the
// offending rows, so we only visit those when checking.
// I.e. other rows are known to be good a priori.
if (!ci.isInvalidated()) {
checkStmt.append(
" --DERBY-PROPERTIES joinStrategy=nestedLoop, " +
" index=null, " +
" validateCheckConstraint=");
checkStmt.append(Long.toString(baseTableCID));
checkStmt.append('\n');
}
checkStmt.append(" WHERE NOT(");
checkStmt.append(cd.getConstraintText());
checkStmt.append(')');
{code}
> Support deferrable constraints
> ------------------------------
>
> Key: DERBY-532
> URL: https://issues.apache.org/jira/browse/DERBY-532
> Project: Derby
> Issue Type: Improvement
> Components: SQL
> Reporter: Jörg von Frantzius
> Assignee: Dag H. Wanvik
> Labels: derby_triage10_11
> Attachments: IndexDescriptor.html, IndexDescriptorImpl.html,
> IndexRowGenerator.html, SortObserver.html, deferredConstraints.html,
> deferredConstraints.html, deferredConstraints.html, deferredConstraints.html,
> deferredConstraints.html, derby-532-allow-pk-unique-1.diff,
> derby-532-allow-pk-unique-1.status, derby-532-check-constraints-1.diff,
> derby-532-check-constraints-1.stat, derby-532-check-constraints-2.diff,
> derby-532-check-constraints-2.stat, derby-532-fix-drop-not-nullable.diff,
> derby-532-fix-drop-not-nullable.status, derby-532-fix-metadata-1.diff,
> derby-532-fix-metadata-1.status, derby-532-import-1.diff,
> derby-532-import-1.status, derby-532-import-2.diff, derby-532-import-3.diff,
> derby-532-import-3.status, derby-532-more-tests-1.diff,
> derby-532-more-tests-1.stat, derby-532-nullableUniqueFix.diff,
> derby-532-nullableUniqueFix.status, derby-532-post-scan-1.diff,
> derby-532-post-scan-1.stat, derby-532-post-scan-2.diff,
> derby-532-post-scan-2.stat, derby-532-post-scan-3.diff,
> derby-532-post-scan-3.stat, derby-532-post-scan-4.diff,
> derby-532-post-scan-4.stat, derby-532-serializable-scan-1.diff,
> derby-532-serializable-scan-2.diff, derby-532-serializable-scan-2.stat,
> derby-532-syntax-binding-dict-1.diff, derby-532-syntax-binding-dict-1.status,
> derby-532-syntax-binding-dict-2.diff, derby-532-syntax-binding-dict-2.status,
> derby-532-syntax-binding-dict-all-1.diff, derby-532-test-speedup.diff,
> derby-532-test-speedup.status,
> derby-532-test-with-default-deferrable-all-over.diff,
> derby-532-testAlterConstraintInvalidation.diff,
> derby-532-testAlterConstraintInvalidation.status, derby-532-unique-pk-1.diff,
> derby-532-unique-pk-1.status, derby-532-unique-pk-2.diff,
> derby-532-unique-pk-3.diff, derby-532-unique-pk-3.status,
> derby-532-upgrade-1.diff, derby-532-upgrade-1.status,
> derby-532-upgrade-1b.diff, derby-532-xa-1.diff, derby-532-xa-2.diff,
> derby-532-xa-3.diff, derby-532-xa-3.status
>
>
> In many situations it is desirable to have constraints checking taking place
> only at transaction commit time, and not before. If e.g. there is a chain of
> foreign key constraints between tables, insert statements have to be ordered
> to avoid constraint violations. If foreign key references are circular, the
> DML has to be split into insert statements and subsequent update statements
> by the user.
> In other words, with deferred constraints checking, life is much easier for
> the user. Also it can create problems with softwares such as
> object-relational mapping tools that are not prepared for statement ordering
> and thus depend on deferred constraints checking.
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