feat: Add support for SpatialJoinFuzzer (facebookincubator#15455)

Summary:

This change adds support for SpatialJoinFuzzer. Spatial Join is sufficiently different from default Join fuzzing that it seemed better to keep it separate rather than shoe horn into our default join fuzzer. 

SpatialJoin has more limited capabilities than regular joins. It does not support:

* Multiple partition strategies
* Grouped execution
* Spilling
* Flipped join order (build/probe swap)


At the moment the fuzzer only generates simple ``Values -> SpatialJoin`` plans.

Limitations
===========

Apart from this the current iteration of the Spatial fuzzer has following limitations that I will try and address in later iterations.

1. Limited support for radius-based spatial joins (used only in ST_Distance predicate case).
2. No support for complex filter expressions beyond spatial predicates
3. No support for TableScan
4. No support for output column reordering/selection (uses all columns)

Another thing to note is that currently it doesnt support either Presto or DuckDB as a source of truth. Support for adding Presto as a reference query runner will come in future iterations.

Reviewed By: jagill

Differential Revision: D86709638

Author: Krishna Pai

velox/docs/develop/testing.rst

@@ -11,5 +11,6 @@ Testing Tools
     testing/join-fuzzer
     testing/memory-arbitration-fuzzer
     testing/row-number-fuzzer
+    testing/spatial-join-fuzzer
     testing/writer-fuzzer
     testing/spark-query-runner.rst

velox/docs/develop/testing/spatial-join-fuzzer.rst

@@ -0,0 +1,118 @@
+====================
+Spatial Join Fuzzer
+====================
+
+Overview
+========
+
+The Spatial Join Fuzzer tests the correctness of the SpatialJoin operator by generating random geometry data and spatial join plans. It verifies that SpatialJoin produces the same results as NestedLoopJoin for equivalent queries.
+
+
+Supported Features
+==================
+
+Join Types
+----------
+
+The fuzzer tests the two join types supported by SpatialJoin (as defined in ``SpatialJoinNode::isSupported()``):
+
+* **INNER** - Only matching rows from both sides
+* **LEFT** - All rows from left side, matched rows from right side
+
+Spatial Predicates
+------------------
+
+The fuzzer tests these spatial predicates:
+
+* ``ST_Intersects(geometry1, geometry2)`` - Tests if geometries intersect
+* ``ST_Contains(geometry1, geometry2)`` - Tests if one geometry contains another
+* ``ST_Within(geometry1, geometry2)`` - Tests if one geometry is within another
+* ``ST_Distance(geometry1, geometry2) < threshold`` - Tests distance with threshold
+
+Geometry Types
+--------------
+
+The fuzzer generates Well-Known Text (WKT) strings for three geometry types:
+
+* **POINT** - Single coordinate point (e.g., ``POINT (10.5 20.3)``)
+* **POLYGON** - Closed shape with vertices
+* **LINESTRING** - Line segment between two points
+
+Distribution Patterns
+---------------------
+
+Geometries are generated using three distribution patterns:
+
+* **Uniform** - Geometries uniformly distributed in space (0-1000 range)
+* **Clustered** - Geometries grouped in 5 specific regions to test overlap scenarios
+* **Sparse** - Geometries widely spread (0-2000 range) with low overlap probability
+
+Implementation Details
+======================
+
+
+Geometry Generation
+-------------------
+
+Geometries are generated using ``AbstractInputGenerator`` subclasses:
+
+* ``PointInputGenerator`` - Generates POINT WKT strings
+* ``PolygonInputGenerator`` - Generates POLYGON WKT strings
+* ``LineStringInputGenerator`` - Generates LINESTRING WKT strings
+
+Each generator implements the ``generate(vector_size_t index)`` method to produce geometry strings based on the distribution pattern.
+
+**Uniform Distribution**::
+
+    x = random(0, 1000)
+    y = random(0, 1000)
+    POINT (x y)
+
+**Clustered Distribution**::
+
+    cluster = row % 5  // 5 clusters
+    centerX = cluster * 200 + 100
+    centerY = cluster * 200 + 100
+    x = centerX + random(-50, 50)
+    y = centerY + random(-50, 50)
+    POINT (x y)
+
+**Sparse Distribution**::
+
+    x = random(0, 2000)  // Larger Range
+    y = random(0, 2000)
+    POINT (x y)
+
+Data Matching Strategy
+----------------------
+
+To ensure some matches occur during joins:
+
+* Build side copies ~30% of geometries from probe side
+* 10% chance of empty build side to test edge cases
+
+Verification
+------------
+
+The fuzzer compares results from two equivalent plans:
+
+1. **SpatialJoin plan** - Using the specialized SpatialJoin operator
+2. **NestedLoopJoin plan** - Using NestedLoopJoin with the same spatial predicate as a filter
+
+Results must match exactly, validating that SpatialJoin implements spatial predicates correctly.
+
+Key Differences from JoinFuzzer
+================================
+
+Join Conditions
+---------------
+
+Unlike regular joins with simple equality predicates::
+
+    // Regular join
+    probe.id = build.id
+
+    // Spatial join
+    ST_Intersects(probe_geom, build_geom)
+
+Spatial joins use **function call expressions** as join conditions rather than simple column references.

velox/exec/fuzzer/CMakeLists.txt

@@ -146,6 +146,19 @@ target_link_libraries(
   velox_expression_test_utility
 )
 
+# Spatial Join Fuzzer.
+add_executable(velox_spatial_join_fuzzer SpatialJoinFuzzerRunner.cpp SpatialJoinFuzzer.cpp)
+
+target_link_libraries(
+  velox_spatial_join_fuzzer
+  velox_type
+  velox_vector_fuzzer
+  velox_fuzzer_util
+  velox_exec_test_lib
+  velox_expression_test_utility
+  velox_vector_test_lib
+)
+
 add_library(velox_writer_fuzzer WriterFuzzer.cpp)
 
 target_link_libraries(