Digging into this more to try to better understand Calcite and hopefully
make
progress,it seems like the query breaks here:

https://github.com/apache/calcite/blob/5b2de4ef5c9447bc9f7aff98dd049bd32af5c53d/core/src/main/java/org/apache/calcite/rel/rel2sql/SqlImplementor.java#L1450-L1454

    @Override protected Context getAliasContext(RexCorrelVariable variable)
{
      return requireNonNull(
          correlTableMap.get(variable.id),
          () -> "variable " + variable.id + " is not found");
    }

Unfortunately, this feature (at least I think so?) is the barrier to
me being able to make efficient cross-datasource queries that return the
right
data shape for GraphQL responses.

My current duct-tape hack is to split the query into query-per-join which I
assume defeats most of Calcite's optimization and planning abilities =(

It's not much, but I'm also willing to offer $250 if anyone could help me
fix
this or figure out an alternative solution.

On Mon, Feb 14, 2022 at 4:26 PM Gavin Ray <[email protected]> wrote:

> Apologies for the slow reply Ruben, I appreciate your help.
> The full stack trace (I was prototyping in sqlline) seems to be more
> helpful:
>
> Here is what seems to be the most useful bits:
> ======================================
> java.sql.SQLException: Error while preparing plan
> [EnumerableCorrelate(correlation=[$cor0], joinType=[inner],
> requiredColumns=[{0}])
>   JdbcToEnumerableConverter
>
> Caused by: java.lang.IllegalStateException: Unable to implement
> EnumerableCorrelate
>     Suppressed: java.lang.NullPointerException: variable $cor0 is not found
> at java.base/java.util.Objects.requireNonNull(Objects.java:334)
> at
> org.apache.calcite.rel.rel2sql.SqlImplementor$BaseContext.getAliasContext(SqlImplementor.java:1429)
> at
> org.apache.calcite.rel.rel2sql.SqlImplementor$Context.toSql(SqlImplementor.java:628)
>                 ....
> at
> org.apache.calcite.rel.rel2sql.RelToSqlConverter.visit(RelToSqlConverter.java:427)
>
> And here is the entire thing:
> ======================================
> java.sql.SQLException: Error while preparing plan
> [EnumerableCorrelate(correlation=[$cor0], joinType=[inner],
> requiredColumns=[{0}])
>   JdbcToEnumerableConverter
>     JdbcTableScan(table=[[hsql, PUBLIC, houses]])
>   EnumerableCollect(field=[EXPR$0])
>     EnumerableProject(id=[$0], name=[$1], todos=[$3])
>       EnumerableCorrelate(correlation=[$cor1], joinType=[inner],
> requiredColumns=[{0}])
>         JdbcToEnumerableConverter
>           JdbcFilter(condition=[=($2, $cor0.id)])
>             JdbcTableScan(table=[[hsql, PUBLIC, users]])
>         EnumerableCollect(field=[EXPR$0])
>           JdbcToEnumerableConverter
>             JdbcProject(id=[$0], description=[$2])
>               JdbcFilter(condition=[=($1, $cor1.id)])
>                 JdbcTableScan(table=[[hsql, PUBLIC, todos]])
> ]
> at org.apache.calcite.avatica.Helper.createException(Helper.java:56)
> at org.apache.calcite.avatica.Helper.createException(Helper.java:41)
> at
> org.apache.calcite.jdbc.CalciteConnectionImpl.prepareStatement_(CalciteConnectionImpl.java:239)
> at
> org.apache.calcite.jdbc.CalciteConnectionImpl.access$100(CalciteConnectionImpl.java:101)
> at
> org.apache.calcite.jdbc.CalciteConnectionImpl$2.prepareStatement(CalciteConnectionImpl.java:188)
> at CalciteSchemaManager.executeQuery(CalciteSchemaManager.kt:209)
> at CalciteSchemaManager.executeQuery(CalciteSchemaManager.kt:213)
> at ForeignKeyTest.throwawayTest(ForeignKeyTest.kt:265)
>
> Caused by: java.lang.IllegalStateException: Unable to implement
> EnumerableCorrelate(correlation=[$cor0], joinType=[inner],
> requiredColumns=[{0}]): rowcount = 22500.0, cumulative cost = {318610.0
> rows, 562611.0 cpu, 0.0 io}, id = 315
>   JdbcToEnumerableConverter: rowcount = 100.0, cumulative cost = {110.0
> rows, 111.0 cpu, 0.0 io}, id = 293
>     JdbcTableScan(table=[[hsql, PUBLIC, houses]]): rowcount = 100.0,
> cumulative cost = {100.0 rows, 101.0 cpu, 0.0 io}, id = 15
>   EnumerableCollect(field=[EXPR$0]): rowcount = 225.0, cumulative cost =
> {2959.0 rows, 5625.0 cpu, 0.0 io}, id = 313
>     EnumerableCalc(expr#0..3=[{inputs}], proj#0..1=[{exprs}],
> todos=[$t3]): rowcount = 225.0, cumulative cost = {2734.0 rows, 5400.0 cpu,
> 0.0 io}, id = 317
>       EnumerableCorrelate(correlation=[$cor1], joinType=[inner],
> requiredColumns=[{0}]): rowcount = 225.0, cumulative cost = {2509.0 rows,
> 3825.0 cpu, 0.0 io}, id = 309
>         JdbcToEnumerableConverter: rowcount = 15.0, cumulative cost =
> {116.5 rows, 202.5 cpu, 0.0 io}, id = 298
>           JdbcFilter(condition=[=($2, $cor0.id)]): rowcount = 15.0,
> cumulative cost = {115.0 rows, 201.0 cpu, 0.0 io}, id = 296
>             JdbcTableScan(table=[[hsql, PUBLIC, users]]): rowcount =
> 100.0, cumulative cost = {100.0 rows, 101.0 cpu, 0.0 io}, id = 16
>         EnumerableCollect(field=[EXPR$0]): rowcount = 15.0, cumulative
> cost = {143.5 rows, 241.5 cpu, 0.0 io}, id = 307
>           JdbcToEnumerableConverter: rowcount = 15.0, cumulative cost =
> {128.5 rows, 226.5 cpu, 0.0 io}, id = 305
>             JdbcProject(id=[$0], description=[$2]): rowcount = 15.0,
> cumulative cost = {127.0 rows, 225.0 cpu, 0.0 io}, id = 303
>               JdbcFilter(condition=[=($1, $cor1.id)]): rowcount = 15.0,
> cumulative cost = {115.0 rows, 201.0 cpu, 0.0 io}, id = 301
>                 JdbcTableScan(table=[[hsql, PUBLIC, todos]]): rowcount =
> 100.0, cumulative cost = {100.0 rows, 101.0 cpu, 0.0 io}, id = 18
>
> at
> org.apache.calcite.adapter.enumerable.EnumerableRelImplementor.implementRoot(EnumerableRelImplementor.java:114)
> at
> org.apache.calcite.adapter.enumerable.EnumerableInterpretable.toBindable(EnumerableInterpretable.java:114)
> at
> org.apache.calcite.prepare.CalcitePrepareImpl$CalcitePreparingStmt.implement(CalcitePrepareImpl.java:1130)
> at
> org.apache.calcite.prepare.CalcitePrepareImpl$CalcitePreparingStmt.prepare_(CalcitePrepareImpl.java:1032)
> at
> org.apache.calcite.prepare.CalcitePrepareImpl$CalcitePreparingStmt.prepareRel(CalcitePrepareImpl.java:988)
> at
> org.apache.calcite.prepare.CalcitePrepareImpl.prepare2_(CalcitePrepareImpl.java:668)
> at
> org.apache.calcite.prepare.CalcitePrepareImpl.prepare_(CalcitePrepareImpl.java:513)
> at
> org.apache.calcite.prepare.CalcitePrepareImpl.prepareSql(CalcitePrepareImpl.java:483)
> at
> org.apache.calcite.jdbc.CalciteConnectionImpl.parseQuery(CalciteConnectionImpl.java:249)
> at
> org.apache.calcite.jdbc.CalciteConnectionImpl.prepareStatement_(CalciteConnectionImpl.java:229)
> ... 88 more
> Suppressed: java.lang.NullPointerException: variable $cor0 is not found
> at java.base/java.util.Objects.requireNonNull(Objects.java:334)
> at
> org.apache.calcite.rel.rel2sql.SqlImplementor$BaseContext.getAliasContext(SqlImplementor.java:1429)
> at
> org.apache.calcite.rel.rel2sql.SqlImplementor$Context.toSql(SqlImplementor.java:628)
> at
> org.apache.calcite.rel.rel2sql.SqlImplementor$Context.toSql(SqlImplementor.java:1069)
> at
> org.apache.calcite.rel.rel2sql.SqlImplementor$Context.callToSql(SqlImplementor.java:776)
> at
> org.apache.calcite.rel.rel2sql.SqlImplementor$Context.toSql(SqlImplementor.java:750)
> at
> org.apache.calcite.rel.rel2sql.RelToSqlConverter.visit(RelToSqlConverter.java:427)
> at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native
> Method)
> at
> java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
> at
> java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
> at java.base/java.lang.reflect.Method.invoke(Method.java:568)
> at org.apache.calcite.util.ReflectUtil$2.invoke(ReflectUtil.java:531)
> at
> org.apache.calcite.rel.rel2sql.RelToSqlConverter.dispatch(RelToSqlConverter.java:139)
> at
> org.apache.calcite.rel.rel2sql.RelToSqlConverter.visitInput(RelToSqlConverter.java:147)
> at
> org.apache.calcite.rel.rel2sql.SqlImplementor.visitInput(SqlImplementor.java:201)
> at
> org.apache.calcite.rel.rel2sql.SqlImplementor.visitInput(SqlImplementor.java:189)
> at
> org.apache.calcite.adapter.jdbc.JdbcToEnumerableConverter.generateSql(JdbcToEnumerableConverter.java:351)
> at
> org.apache.calcite.adapter.jdbc.JdbcToEnumerableConverter.implement(JdbcToEnumerableConverter.java:107)
> at
> org.apache.calcite.adapter.enumerable.EnumerableRelImplementor.visitChild(EnumerableRelImplementor.java:104)
> at
> org.apache.calcite.adapter.enumerable.EnumerableCorrelate.implement(EnumerableCorrelate.java:113)
> at
> org.apache.calcite.adapter.enumerable.EnumerableRelImplementor.visitChild(EnumerableRelImplementor.java:104)
> at
> org.apache.calcite.adapter.enumerable.EnumerableCalc.implement(EnumerableCalc.java:118)
> at
> org.apache.calcite.adapter.enumerable.EnumerableRelImplementor.visitChild(EnumerableRelImplementor.java:104)
> at
> org.apache.calcite.adapter.enumerable.EnumerableCollect.implement(EnumerableCollect.java:81)
> at
> org.apache.calcite.adapter.enumerable.EnumerableRelImplementor.visitChild(EnumerableRelImplementor.java:104)
> at
> org.apache.calcite.adapter.enumerable.EnumerableCorrelate.implement(EnumerableCorrelate.java:139)
> at
> org.apache.calcite.adapter.enumerable.EnumerableRelImplementor.implementRoot(EnumerableRelImplementor.java:111)
> ... 97 more
>
> On Mon, Feb 14, 2022 at 1:14 PM Ruben Q L <[email protected]> wrote:
>
>> Hello Gavin,
>>
>> what's the full stack trace that you get?
>>
>> On Mon, Feb 14, 2022 at 3:24 PM Gavin Ray <[email protected]> wrote:
>>
>> > The following query seems to work perfectly:
>> >
>> > SELECT
>> >     "houses"."id",
>> >     "houses"."name",
>> >     "houses"."address",
>> >     ARRAY(
>> >         SELECT
>> >             "users"."id",
>> >             "users"."name"
>> >         FROM
>> >             "users"
>> >         WHERE
>> >             "users"."house_id" = "houses"."id"
>> >     ) AS "users"
>> > FROM
>> >     "houses";
>> >
>> > However, if I modify the inner ARRAY() query for "users" to be:
>> >
>> > SELECT
>> >     "users"."id",
>> >     "users"."name",
>> >     ARRAY(
>> >         SELECT
>> >             "todos"."id",
>> >             "todos"."description"
>> >         FROM
>> >             "todos"
>> >         WHERE
>> >             "todos"."user_id" = "users"."id"
>> >     ) AS "todos"
>> > FROM
>> >     "users"
>> >
>> > ===================================================
>> >
>> > Unable to implement EnumerableNestedLoopJoin(condition=[true],
>> > joinType=[inner]): rowcount = 22500.0, cumulative cost = {227855.0 rows,
>> > 18242.0 cpu, 0.0 io}, id = 12787
>> >   EnumerableTableScan(table=[[example, houses]]): rowcount = 100.0,
>> > cumulative cost = {100.0 rows, 101.0 cpu, 0.0 io}, id = 12718
>> >   EnumerableCollect(field=[x]): rowcount = 225.0, cumulative cost =
>> {2755.0
>> > rows, 18141.0 cpu, 0.0 io}, id = 12785
>> >     EnumerableCalc(expr#0..3=[{inputs}], proj#0..1=[{exprs}],
>> todos=[$t3]):
>> > rowcount = 225.0, cumulative cost = {2530.0 rows, 17916.0 cpu, 0.0 io},
>> id
>> > = 12793
>> >       EnumerableCorrelate(correlation=[$cor1], joinType=[inner],
>> > requiredColumns=[{0}]): rowcount = 225.0, cumulative cost = {2305.0
>> rows,
>> > 16341.0 cpu, 0.0 io}, id = 12781
>> >         EnumerableCalc(expr#0..2=[{inputs}], expr#3=[$cor0], expr#4=[$
>> > t3.id],
>> > expr#5=[=($t2, $t4)], proj#0..2=[{exprs}], $condition=[$t5]): rowcount =
>> > 15.0, cumulative cost = {115.0 rows, 1101.0 cpu, 0.0 io}, id = 12789
>> >           EnumerableTableScan(table=[[example, users]]): rowcount =
>> 100.0,
>> > cumulative cost = {100.0 rows, 101.0 cpu, 0.0 io}, id = 12722
>> >         EnumerableCollect(field=[x]): rowcount = 15.0, cumulative cost =
>> > {130.0 rows, 1016.0 cpu, 0.0 io}, id = 12779
>> >           EnumerableCalc(expr#0..2=[{inputs}], expr#3=[$cor1], expr#4=[$
>> > t3.id], expr#5=[=($t1, $t4)], id=[$t0], description=[$t2],
>> > $condition=[$t5]): rowcount = 15.0, cumulative cost = {115.0 rows,
>> 1001.0
>> > cpu, 0.0 io}, id = 12797
>> >             EnumerableTableScan(table=[[example, todos]]): rowcount =
>> > 100.0, cumulative cost = {100.0 rows, 101.0 cpu, 0.0 io}, id = 12728
>> > (state=,code=0)
>> >
>>
>

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