It looks like the operation is done by
1. Build main query
* `main query= builder.scan(table name).build`
2. Then push the main table
* `builder.push(main query)`
3. Build subquery
* `sub query = builder.scan().filter().build`
4. Push the subquery
* `builder.push(sub query)`
5. Then do semi-join operation on the condition field
* `builder.semiJoin(builder.equals(builder.filed(...filed name),
builder.filed(...field name)))`
Thanks for the suggestion, it's very helpful!
On Tue, 25 Jun 2019 at 23:26, Haisheng Yuan <h.y...@alibaba-inc.com> wrote:
>
> The input parameter of semiJoin method should be join conditions, not just
> fields.
> Check the example usage in RelMetadataTest.java#checkPredicates L1435.
>
> - Haisheng
>
> ------------------------------------------------------------------
> 发件人：Chia-Hung Lin<cli...@googlemail.com.INVALID>
> 日 期：2019年06月26日 05:38:30
> 收件人：<dev@calcite.apache.org>
> 主 题：How to do SemiJoin?
>
> A quick question. I am trying to do semiJoin(). The code looks like below.
>
> val subquery = builder.
> scan("foodmart", "customer").
> filter(builder.equals(builder.field("city"),
> builder.literal("Albany"))).
> project(builder.field("customer_id")).
> build
>
> val mainquery = builder.
> scan("foodmart", "sales_fact_1998").
> project(builder.field("unit_sales")).
> build
>
> val relnode = builder.push(mainquery).push(subquery).semiJoin(
> builder.field("customer_id")
> ).build
>
> But when executing, it throws an error message saying
> `java.lang.RuntimeException: java.sql.SQLException: Error while
> preparing statement [null]`, and following another exception that
> mentions
>
> Cause: org.codehaus.commons.compiler.CompileException: Line 18, Column
> 66: No applicable constructor/method found for actual parameters
> "java.math.BigDecimal"; candidates are: "public static boolean
> org.apache.calcite.runtime.SqlFunctions.isTrue(java.lang.Boolean)"
>
> Although it looks like code generation issue, I suspect it's more
> likely my incorrect usage to construct semiJoin function. What is the
> correct way to use semiJoin? Is there any example or doc that may
> contain related info? I have this question because I can not find such
> info after searching on the internet. Most of semiJoin results found
> on the internet are internal implementation which looks like not
> related to the usage.
>
> Thanks
