[Analytics] Vendor the liquid-cache library crates

[cocosz]

Description

Vendors the liquid-cache library as a self-contained Cargo workspace under sandbox/plugins/liquid-cache/src/main/rust:

• opensearch-liquid-cache-core — the in-memory decoded-batch cache.
• opensearch-liquid-cache-datafusion — the DataFusion parquet reader that serves from / populates the cache.

These crates build and unit-test on their own and are not yet wired into the engine. The analytics backend compiles them in only when built with the liquid_cache cargo feature introduced in the parent PR, which the follow-up integration PR enables.

Kept as its own PR so the vendored library can be reviewed in isolation, separate from the seam and from the engine/Java wiring.

This is PR 2 of a 3-part stack:

1. Seam ([Analytics] Add optional liquid cache seam for indexed parquet scans (cargo feature) #22553): feature-gated in-process hook (no-op by default).
2. This PR — library: vendors the liquid-cache crates in isolation.
3. Integration ([Analytics] Wire liquid cache into the analytics engine (plugin + integration) #22595): wires the library into the engine + Java plugin + integration test.

Changes

• 53 files under sandbox/plugins/liquid-cache/src/main/rust (the two crates + workspace Cargo.toml, Cargo.lock, rust-toolchain.toml).
• sandbox/plugins/liquid-cache/.gitignore.

54 files changed, +12,433. No build.gradle is added, so the Gradle build ignores the directory and the crates stay dormant until the integration PR wires them in.

Check List

• Library workspace builds and unit-tests standalone via cargo test.
• Not referenced by any Gradle build yet (dormant until [Analytics] Wire liquid cache into the analytics engine (plugin + integration) #22595).
• API changes companion PR raised (n/a).
• Public documentation issue/PR created (n/a — sandbox).

Note: PRs target main. Stacked on #22553 — review/merge order: #22553 → this PR → #22595.

[github-actions]

PR Code Analyzer ❗

AI-powered 'Code-Diff-Analyzer' found issues on commit eb9aff4.

⛔ Hard block: Issues at Medium severity or above will block this PR from merging.

Path	Line	Severity	Description
sandbox/plugins/analytics-backend-datafusion/rust/Cargo.toml	0	high	MANDATORY DEPENDENCY FLAG: New external crate 'base64 = "0.22"' added. Base64 encoding has no apparent role in a Parquet in-memory cache layer; its presence is anomalous and warrants verification — base64 is a common primitive in credential harvesting and data exfiltration payloads. Maintainers must verify this dependency is actually used and for what purpose.
sandbox/plugins/liquid-cache/src/main/rust/Cargo.toml	0	high	MANDATORY DEPENDENCY FLAG: New Cargo workspace introduces 13+ external crates including arrow=58.3.0, parquet=58.3.0, datafusion=54.0.0, tokio=1.52.3, object_store=0.13.2, serde=1.0.228, ahash=0.8.12, congee=0.4.1, fastlanes=0.5.2, tempfile=3.27.0 and others. Each crate is an independent supply chain trust decision. Artifact authenticity cannot be verified from diff alone.
sandbox/plugins/liquid-cache/src/main/rust/Cargo.toml	0	high	MANDATORY DEPENDENCY FLAG: 'congee = "0.4.1"' is a low-profile ART (Adaptive Radix Tree) index crate with limited ecosystem visibility. Obscure crates with small maintainer bases carry elevated namespace hijacking and typosquatting risk. Verify crate owner identity and audit published artifact against source.
sandbox/plugins/liquid-cache/src/main/rust/Cargo.toml	0	high	MANDATORY DEPENDENCY FLAG: 'fastlanes = "0.5.2"' is a niche SIMD bit-packing compression crate. Low-profile crates are disproportionately targeted in supply chain attacks. Verify crate provenance and published artifact integrity independently.
sandbox/plugins/liquid-cache/src/main/rust/datafusion/src/reader/plantime/row_filter.rs	0	medium	Unsafe std::mem::transmute reinterprets a &parquet::arrow::ProjectionMask as a locally-defined mirror struct ProjectionMaskLiquid to read private fields. If the upstream struct layout ever diverges (padding, field reordering, version bump) this produces undefined behavior and arbitrary memory reads. In an adversarial context this pattern can be used to craft a read gadget targeting adjacent heap memory. The technique bypasses the intentional API boundary of the parquet crate.
sandbox/plugins/liquid-cache/src/main/rust/datafusion/src/utils.rs	0	medium	Extensive unsafe raw pointer arithmetic in the BMI2 PDEP fast-path: manual pointer-width reads/writes without bounds checking under #[target_feature(enable="bmi2")]. A logic error or deliberate miscalculation in stride/offset arithmetic yields out-of-bounds reads or writes into the Arrow buffer heap, potentially leaking adjacent decoded column data across tenant queries in a multi-tenant deployment.
sandbox/plugins/liquid-cache/src/main/rust/core/Cargo.toml	1	medium	Provenance comment names an external unreviewed fork: 'https://github.com/cocosz/liquid-cache branch lc-opensearch-df54-v2 commit 8311bccc258756127adbebee3e54140b60fc09ba'. The vendored code originates from a personal GitHub fork, not an upstream release artifact. The named commit has not been verified against any published release. This is a supply chain insertion point — the fork could contain modifications absent from any public audit trail.
sandbox/libs/dataformat-native/build.gradle	0	medium	Feature is silently activated by environment variable LIQUID_CACHE=1 in addition to the declared build property. An attacker with ability to inject environment variables into the build or runtime environment (CI/CD pipeline compromise, container escape) can activate this code path without any source-visible configuration change. Hidden activation vectors are a hallmark of logic bomb deployment.
sandbox/plugins/liquid-cache/src/main/rust/datafusion/src/source.rs	0	low	Process-global cache state is held in a LazyLock (and similar static). In a JVM-embedded native plugin this means cache contents survive across logical request boundaries for the lifetime of the JVM process. A poisoned or unexpectedly large cache entry affects all subsequent queries globally with no isolation boundary.
sandbox/plugins/liquid-cache/src/main/rust/datafusion/src/source.rs	0	low	Cache population is offloaded via tokio::spawn background tasks that are never awaited. Errors from background fills are silently dropped. In an adversarial scenario, a crafted input that triggers fill failures repeatedly could cause cache starvation while masking the root cause, or background tasks could accumulate unboundedly under high query load (resource exhaustion).

The table above displays the top 10 most important findings.

Total: 10 | Critical: 0 | High: 4 | Medium: 4 | Low: 2

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