feat: GeoArrow support for bulk ingestion (GEOGRAPHY/GEOMETRY)

[jatorre]

Summary

Adds geospatial column support to the Snowflake ADBC driver's bulk ingestion path. When Arrow columns carry geoarrow.wkb or geoarrow.wkt extension metadata, the driver automatically creates GEOGRAPHY or GEOMETRY columns in Snowflake and converts the data.

• Detects geoarrow columns from ARROW:extension:name field metadata (handles C Data Interface where Go-level extension types are stripped)
• New statement option adbc.snowflake.statement.ingest_geo_type: "geography" (default, WGS84/4326) or "geometry" (any SRID)
• Extracts SRID from geoarrow CRS metadata (PROJJSON or "EPSG:NNNN" format) for GEOMETRY columns
• Unit tests for type mapping and SRID extraction

How it works

1. Bulk ingest loads data as BINARY via the existing Parquet → PUT → COPY INTO pipeline (unchanged)
2. After COPY, geoarrow columns are detected and converted via CTAS with TO_GEOGRAPHY/TO_GEOMETRY
3. For GEOMETRY columns, SRID is applied via ST_SETSRID if present in geoarrow metadata

Why CTAS instead of direct COPY INTO GEOGRAPHY?

Snowflake's COPY INTO from Parquet cannot load WKB directly into GEOGRAPHY/GEOMETRY columns — only CSV and JSON/AVRO support direct geospatial loading from stages (docs). The CTAS workaround (rename → CTAS with conversion → drop staging) adds minimal overhead at scale.

A future optimization could use COPY transforms (SELECT ... FROM @stage) to convert inline.

Benchmark results

Tested with Czech Republic OSM Geofabrik data (real-world geometries):

Dataset	Rows	Throughput	Geometry type
POIs	465,280	38,119 rows/sec	Point
Roads	1,885,651	56,804 rows/sec	LineString
Buildings	5,014,886	68,611 rows/sec	Polygon

Export (not in this PR)

Export/read-path geoarrow support is not included. Detecting GEOGRAPHY/GEOMETRY columns on the read path is non-trivial because:

• With GEOGRAPHY_OUTPUT_FORMAT=EWKB, srcMeta.Type becomes "binary" (type info lost)
• With default GeoJSON format, srcMeta.Type is "object" (same as VARIANT/OBJECT)

This is related to the broader SRID/CRS propagation discussion across ADBC drivers:

• adbc-drivers/redshift#2 — SRID from EWKB
• adbc-drivers/databricks#350 — geoarrow.wkb conversion

For GEOGRAPHY, CRS is always EPSG:4326. For GEOMETRY, SRID requires data buffering to extract — a common challenge that would benefit from a cross-driver solution.

Context

This is part of a broader effort to add GeoArrow support across ADBC drivers. Previously opened as apache/arrow-adbc#4114, moved here per maintainer request.

Test plan

• Unit tests for toSnowflakeType with geoarrow extension types
• Unit tests for extractSRIDFromMeta (PROJJSON, simple EPSG string, null, empty, invalid)
• Existing TestIngestBatchedParquetWithFileLimit still passes
• End-to-end tested against real Snowflake with points, lines, and polygons
• Verified GEOGRAPHY column type created in Snowflake via INFORMATION_SCHEMA

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