[ShawnChen-Sirius]

Summary

Add the optional com.clickhouse.chdb:chdb-arrow module using Arrow Java 19.0.0 and the native Arrow C Data/C Stream ABI. This PR pins the published chdb-core v26.11.0-rc.3 across four platform packages, with checksums from the release and a header copied from its tarball. The binding's development version becomes 1.0.0-rc.3-SNAPSHOT; this PR does not publish it. Existing JDBC ResultSet/RowBinary semantics and the ordinary JDBC dependency tree are unchanged.

A1–A6

• A1: caller-owned VectorSchemaRoot current batch as an in-memory SQL source with a closable registration and opaque arrowstream('name') fragment.
• A2: one-shot Apache Arrow ArrowReader as a lazily consumed source; the registration owns the reader and holds its C Stream until scans finish before unregistering.
• A3: core-materialized Arrow C Stream result exposed as a typed Arrow Java reader, retaining schema for zero rows.
• A4: ArrowQuery pulls typed batches incrementally, with partial-consumption close, cooperative cancel, and connection/native handle leases.
• A5: synchronous insert into an existing table from a batch or reader through chdb_insert_arrow_stream; source columns must have distinct names and the destination identifier is validated and quoted. No implicit table creation or transaction guarantee.
• A6: pinned core/JNI ABI and platform manifests, Java 11 optional module, explicit Arrow output type choices, ownership rules, and no implicit IPC or unconditional zero-copy claim.

Verification

• Published v26.11.0-rc.3 macOS arm64 asset SHA-256 7b0ea049efcf75a851e744c7d74325d7a9b143227f9b72097e5df252564e3d58; local extraction, header, and staged JNI pair verified without skipEngineVersionCheck.
• On that published pair, JDK 11 and 21 each pass 21/22 Arrow cases; one explicitly disabled regression documents a core String → Int64 silent conversion (upstream issue to be filed separately). JDBC unit tests: 178; the complete JDBC integration suite on JDK 11/macOS arm64: 177. The first sandboxed run could not execute ps for an RSS test; the approved rerun passed.
• LicenseInventoryIT matches 1081 components generated from the rc.3 binary; the only difference from rc.2 is removal of gdeflate (Apache), with no copyleft change.
• PR build.yml runs the native Arrow suite on Linux x86_64/aarch64 and macOS arm64/x86_64 × JDK 11/17/21/25, with no rc.2 skip or engine-version override. A Maven failure fails its platform job and Arrow reports/crash logs are archived. These remote combinations remain to be observed on this PR.

Limits and follow-up

The disabled insert-conversion regression is not counted as passed. It was reproduced on the published rc.3 macOS arm64 library: an Arrow UTF-8 id="not-an-integer" inserted into Int64 reports one row written and stores 0, while equivalent ordinary SQL rejects it with CANNOT_PARSE_TEXT. Re-enable the regression after core resolves that behavior; do not silently coerce in Java. A2 is one-shot; A4 cancellation waits for an in-flight fetch; A5 targets existing tables. Production use and a subsequent Java RC still require review of this PR's four-platform results and the normal publishing gates.

Note

Add chdb-arrow module and bump engine baseline to v26.11.0-rc.3

• Adds an optional chdb-arrow module: ArrowSession provides materialized and incremental Arrow queries, registered Arrow sources, and synchronous Arrow inserts, with ArrowOptions controlling type-mapping flags (default maps String as string)
• Implements the native side in chdb_jni.cpp: JNI entrypoints for materialized queries, stream open/fetch/cancel/close, registration, and insertion, backed by Arrow stream handles (kind 5)
• ChdbConnection tracks Arrow queries and cleanup hooks; close() closes tracked queries and runs hooks before closing statements
• Pins the engine to 26.11.0-rc.3 (SHA-256 values and license inventory updated) and bumps the JNI ABI from 2 to 3; CI runs the Arrow integration tests per Java version
• Risk: JNI ABI bump to 3 means older native shims fail to load; ChdbConnection.arrowStreamOpenNative holds the statement slot for the stream's lifetime, so an unclosed Arrow stream blocks other statements

^{Macroscope summarized 6e9f393.}