[
https://issues.apache.org/jira/browse/CALCITE-4559?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17324339#comment-17324339
]
Julian Hyde edited comment on CALCITE-4559 at 4/17/21, 7:31 PM:
----------------------------------------------------------------
[~danny0405], I am not set on the interfaces of {{RelRule}} which build
operands. This is my first attempt, and I'm happy if others improve them. The
{{Done}} type will not appear in code that builds operands (when someone is
registering a rule) so I don't think it's name is very important; feel free to
improve it. It's probably best if we start with a minimal set of methods
(without {{oneInput}}); we can easily add methods later.
I have a greater concern with the API that applies rules. For example, should
it include {{NullAs}}? We may be able to cover a lot of null behavior
automatically based on strongness: e.g. {{f(x)}} returns null *only if* {{x}}
is null; f(x) returns null *if* {{x}} is null. Many functions are like {{f}}
and we do not need to say anything else about their behavior with nulls.
was (Author: julianhyde):
I am not set on the interfaces of {{RelRule}} which build operands. This is my
first attempt, and I'm happy if others improve them. The {{Done}} type will not
appear in code that builds operands (when someone is registering a rule) so I
don't think it's name is very important; feel free to improve it. It's probably
best if we start with a minimal set of methods (without {{oneInput}}); we can
easily add methods later.
> Create 'interface RexRule', a modular rewrite for row-expressions
> -----------------------------------------------------------------
>
> Key: CALCITE-4559
> URL: https://issues.apache.org/jira/browse/CALCITE-4559
> Project: Calcite
> Issue Type: Bug
> Reporter: Julian Hyde
> Assignee: Julian Hyde
> Priority: Major
>
> We propose to add {{class RexRule}}, a rewrite rule for row-expressions
> ({{class RexNode}}).
> {{class RexRule}} is analogous to how {{class RelRule}} (and the older
> {{class RelOptRule}}) operates on relational expressions ({{interface
> RelNode}}). Also, {{class RexRuleProgram}} is analogous to {{HepProgram}} and
> {{VolcanoPlanner}} (it indexes rules so that we do not have to try every rule
> against every part of the expression). And a rule describes which operands it
> matches using {{RexRule.describe(RexRule.OperandBuilder)}}, similar to
> calling {{RelRule.Config.operandSupplier().apply()}}.
> The advantages of {{RexRule}} are similar to {{RelRule}}: rules can be
> defined in a modular way, can be documented and tested individually, and can
> be enabled individually.
> The rules could be applied in various ways. {{RelBuilder.Config}} could
> contain a {{RexRuleProgram}} that would be applied every time an expression
> is simplified by a {{RelBuilder}}. There could also be a sub-class of
> {{interface RelShuttle}} that applies the rules to every {{RexNode}} in a
> tree (e.g. inside {{Filter}}, {{Project}} and {{Join}}).
> I don't yet know whether, or how, rules might support 3-valued boolean logic
> ({{RexUnknownAs}}). For example, a rule that simplifies "x = x" to "TRUE" is
> valid in an "unknownAsFalse" context (e.g. as top-level of {{Filter}}
> condition), but not in an "unknownAsUnknown" context (e.g. in {{Project}}
> expression).
> This case is related to CALCITE-3470 (making relational and row-expression
> rules more similar, as in CockroachDB), but would deliver an API rather than
> a textual DSL.
--
This message was sent by Atlassian Jira
(v8.3.4#803005)
