Bug Report: PulloutSubquery has missing bind var __sq_has_values1

[frouioui]

Overview of the Issue

When executing a sharded query with an EXISTS using the Gen4 planner, VTTablet produces the following error: missing bind var __sq_has_values1. The v3 planner does not fail.

The issue was first seen in #9710 when changing VTGate's default planner. The test TestExplain started failing (See failure in CI) with the selectsharded query:

select name from user where exists (select id from t1) /* non-correlated subquery as EXISTS */;

The plan for the query above is:

{
  "QueryType": "SELECT",
  "Original": "select name from user where exists (select id from t1)",
  "Instructions": {
    "OperatorType": "Subquery",
    "Variant": "PulloutExists",
    "PulloutVars": [
      "__sq_has_values1"
    ],
    "Inputs": [
      {
        "OperatorType": "Route",
        "Variant": "Scatter",
        "Keyspace": {
          "Name": "zlookup_unique",
          "Sharded": true
        },
        "FieldQuery": "select id from t1 where 1 != 1",
        "Query": "select id from t1",
        "Table": "t1"
      },
      {
        "OperatorType": "Route",
        "Variant": "Scatter",
        "Keyspace": {
          "Name": "user",
          "Sharded": true
        },
        "FieldQuery": "select `name` from `user` where 1 != 1",
        "Query": "select `name` from `user` where :__sq_has_values1",
        "Table": "`user`"
      }
    ]
  }
}

The issue is also reproducible with the local examples.

Reproduction Steps

1. Deploy a sharded Vitess cluster using the examples
2. Run the following query:

select /*vt+ PLANNER=gen4 */ order_id from corder where exists (select customer_id from customer);

3. The output should contain the error:

ERROR 1105 (HY000): target: customer.-80.primary: vttablet: rpc error: code = InvalidArgument desc = missing bind var __sq_has_values1 (CallerID: userData1)
target: customer.80-.primary: vttablet: rpc error: code = InvalidArgument desc = missing bind var __sq_has_values1 (CallerID: userData1)

Binary Version

main

Operating System and Environment details

MacOS

Log Fragments

No response