MDEV-39813 ST_GeomFromGeoJSON does not control recursion depth

[grooverdan]

Using stack_p wasn't a portable concept in 12.3 when JSON parsing got unlimited depth. To let ST_GeomFromGeoJSON as a recursive function, needed because object order of "type" may be after the "geometries", some stack checking was required.

Use the check_stack_depth function to allow excessively deep GeoJSON objects to error.

@mariadb-RuchaDeodhar , I'm after a concept approval. To run reliably I'm going to move this test to the thread_stack_overun.test that @vaintroub added in 10.11 (#5320) that hasn't yet been merged up.

The 10.6/10.11 fix for this bug is going to change the stack_p, killed_ptr and json_scan_start but what is clear is that 12.3 requires a stack overrun check.

[gemini-code-assist]

Code Review

This pull request re-enables the gis-json test and addresses a potential infinite recursion issue in Geometry::create_from_json by adding a stack overrun check using check_stack_overrun. Unused variables related to the JSON engine's stack pointer were also cleaned up. The review feedback recommends refactoring Geometry::create_from_json to accept THD *thd as a parameter rather than calling current_thd internally, which avoids costly thread-local lookups during recursive execution.

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[gemini-code-assist]

Calling current_thd (which performs a thread-local lookup) inside the recursive function Geometry::create_from_json can introduce significant performance overhead, especially since this function is executed per-record and recursively for nested JSON structures.

According to the project's performance guidelines, thread-local lookups should be avoided in performance-critical paths.

Recommendation

Consider refactoring Geometry::create_from_json to accept THD *thd as its first parameter:

static Geometry *create_from_json(THD *thd,
                                  Geometry_buffer *buffer,
                                  json_engine_t *je,
                                  bool er_on_3D,
                                  String *res);

This allows the caller (e.g., Item_func_geomfromgeojson::val_str) to retrieve current_thd once and pass it down, avoiding repeated thread-local lookups during recursion.

Additionally, there is an extra space before the comma in STACK_MIN_SIZE , NULL which has been cleaned up in the suggestion below.

  if (check_stack_overrun(thd, STACK_MIN_SIZE, NULL))
    return NULL;

References

1. Avoid calling thread-local lookups like current_thd or thd_to_trx in performance-critical paths (such as per-record operations or frequent lookups). Instead, pass down or cache the transaction pointer (trx_t) to reduce overhead.