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https://issues.apache.org/jira/browse/CALCITE-1887?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16121686#comment-16121686
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Jens Lehmann commented on CALCITE-1887:
---------------------------------------
While we do not have the knowledge / resources to fix the problem ourselves at
the moment, the corresponding SPARK PR (linked above) has made progress and we
would appreciate any help.
> Detect transitive join conditions via expressions
> -------------------------------------------------
>
> Key: CALCITE-1887
> URL: https://issues.apache.org/jira/browse/CALCITE-1887
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Affects Versions: 1.13.0
> Reporter: Claus Stadler
> Assignee: Julian Hyde
>
> Given table aliases ta, tb column names ca, cb, and an arbitrary
> (deterministic) expression expr then calcite should be capable to infer join
> conditions by transitivity:
> {noformat}
> ta.ca = expr AND tb.cb = expr -> ta.ca = tb.cb
> {noformat}
> The use case for us stems from SPARQL to SQL rewriting, where SPARQL queries
> such as
> {code:java}
> SELECT {
> dbr:Leipzig a ?type .
> dbr:Leipzig dbo:mayor ?mayor
> }
> {code}
> result in an SQL query similar to
> {noformat}
> SELECT s.rdf a, s.rdf b WHERE a.s = 'dbr:Leipzig' AND b.s = 'dbr:Leipzig'
> {noformat}
> A consequence of the join condition not being recognized is, that Apache
> Flink does not find an executable plan to process the query.
> Self contained example:
> {code:java}
> package my.package;
> import org.apache.calcite.adapter.java.ReflectiveSchema;
> import org.apache.calcite.plan.RelOptUtil;
> import org.apache.calcite.rel.RelNode;
> import org.apache.calcite.rel.RelRoot;
> import org.apache.calcite.schema.SchemaPlus;
> import org.apache.calcite.sql.SqlNode;
> import org.apache.calcite.sql.parser.SqlParser;
> import org.apache.calcite.tools.FrameworkConfig;
> import org.apache.calcite.tools.Frameworks;
> import org.apache.calcite.tools.Planner;
> import org.junit.Test;
> public class TestCalciteJoin {
> public static class Triple {
> public String s;
> public String p;
> public String o;
> public Triple(String s, String p, String o) {
> super();
> this.s = s;
> this.p = p;
> this.o = o;
> }
> }
> public static class TestSchema {
> public final Triple[] rdf = {new Triple("s", "p", "o")};
> }
> @Test
> public void testCalciteJoin() throws Exception {
> SchemaPlus rootSchema = Frameworks.createRootSchema(true);
> rootSchema.add("s", new ReflectiveSchema(new TestSchema()));
> Frameworks.ConfigBuilder configBuilder =
> Frameworks.newConfigBuilder();
> configBuilder.defaultSchema(rootSchema);
> FrameworkConfig frameworkConfig = configBuilder.build();
> SqlParser.ConfigBuilder parserConfig =
> SqlParser.configBuilder(frameworkConfig.getParserConfig());
> parserConfig
> .setCaseSensitive(false)
> .setConfig(parserConfig.build());
> Planner planner = Frameworks.getPlanner(frameworkConfig);
> // SELECT s.rdf a, s.rdf b WHERE a.s = 5 AND b.s = 5
> SqlNode sqlNode = planner.parse("SELECT * FROM \"s\".\"rdf\" \"a\",
> \"s\".\"rdf\" \"b\" WHERE \"a\".\"s\" = 5 AND \"b\".\"s\" = 5");
> planner.validate(sqlNode);
> RelRoot relRoot = planner.rel(sqlNode);
> RelNode relNode = relRoot.project();
> System.out.println(RelOptUtil.toString(relNode));
> }
> }
> {code}
> Actual plan:
> {code:java}
> LogicalProject(s=[$0], p=[$1], o=[$2], s0=[$3], p0=[$4], o0=[$5])
> LogicalFilter(condition=[AND(=($0, 5), =($3, 5))])
> LogicalJoin(condition=[true], joinType=[inner])
> EnumerableTableScan(table=[[s, rdf]])
> EnumerableTableScan(table=[[s, rdf]])
> {code}
> Expected Plan fragment:
> {code:java}
> LogicalJoin(condition=[=($0, $3)], joinType=[inner])
> {code}
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