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https://issues.apache.org/jira/browse/CALCITE-4783?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17416527#comment-17416527
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xzh_dz commented on CALCITE-4783:
---------------------------------
[~julianhyde]
Thanks, In my project, i always use `RelFieldTrimmer` to trim unused fields.
In this case,there is no predicate condition `ename = '1'` in final
RelNode(trimmed).
> Dropped the predicate condition after RelFieldTrimmer trim the RelNode
> ----------------------------------------------------------------------
>
> Key: CALCITE-4783
> URL: https://issues.apache.org/jira/browse/CALCITE-4783
> Project: Calcite
> Issue Type: Improvement
> Reporter: xzh_dz
> Priority: Major
>
> {code:java}
> // code placeholder
> org.apache.calcite.test.SqlToRelConverterTest
> @Test void testTrim() {
> final String sql = "select count(*) from emp where ename = '1'";
> final RelNode rel = tester.convertSqlToRel(sql).rel;
> final HepProgramBuilder programBuilder = HepProgram.builder();
> programBuilder.addRuleInstance(CoreRules.FILTER_TO_CALC);
> final HepPlanner planner = new HepPlanner(programBuilder.build());
> planner.setRoot(rel);
> final RelNode calc = planner.findBestExp();
> final List<RelOptTable> relOptTables = RelOptUtil.findAllTables(calc);
> RelOptSchema relOptSchema = null;
> if (relOptTables.size() != 0) {
> relOptSchema = relOptTables.get(0).getRelOptSchema();
> }
> final RelBuilder relBuilder = RelFactories.LOGICAL_BUILDER.create(
> calc.getCluster(), relOptSchema);
> final RelFieldTrimmer fieldTrimmer = new RelFieldTrimmer(null, relBuilder);
> final RelNode trimmed = fieldTrimmer.trim(calc);
> System.out.println(RelOptUtil.toString(trimmed));
> }
> rel:
> LogicalAggregate(group=[{}], EXPR$0=[COUNT()])
> LogicalProject($f0=[0])
> LogicalFilter(condition=[=($1, '1')])
> LogicalTableScan(table=[[CATALOG, SALES, EMP]])
> trimmed(After RelFieldTrimmer):
> LogicalAggregate(group=[{}], EXPR$0=[COUNT()])
> LogicalTableScan(table=[[CATALOG, SALES, EMP]]){code}
> Compared with RelNode, we can find that there is no predicate condition ename
> = '1'.
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