Delta Lake is a transactional table format and multi-engine connector suite. In production it writes Parquet data files alongside a JSON transaction log (`_delta_log`) and periodic checkpoints; every commit is an atomic append of log actions. Readers reconstruct table snapshots by replaying the log and checkpoints, enabling ACID operations, time travel, schema evolution, and incremental streaming on object storage. This repository is the reference implementation of that protocol, not an end-user data platform. The architecture is a multi-module Scala/Java/Python monorepo: `spark/` contains the Spark V1 and V2 connectors plus SQL extensions; `kernel/` is a standalone Java, engine-agnostic library exposing `Engine`, `TableManager`, `TransactionBuilder`, and a default Hadoop engine; `storage/` provides LogStore abstractions and cloud-specific commit coordination; and `flink/`, `iceberg/`, `sharing/`, and `python/delta` provide additional engine integrations. Key entry points are `DeltaTable`, `DeltaSparkSessionExtension`, `io.delta.kernel.TableManager`, and Flink's `DeltaDynamicTableSource`/`DeltaDynamicTableSink`. The central data flow is client -> `OptimisticTransaction`/Kernel `Transaction` -> log action -> LogStore commit; reads use `Snapshot`/`SnapshotBuilder` to replay log actions. External dependencies include Apache Spark, Hadoop FileSystem, Parquet, Jackson, and optional cloud SDKs. Maintenance is genuinely active: recent commits, CI matrices for Spark 4.0-4.2, Flink, Iceberg, Kernel, and Unity Catalog, plus a large compatibility test suite. The codebase nevertheless carries transitional complexity: a V2/Kernel-backed Spark connector coexists with the legacy V1 path, many Spark-version shims exist, test suites are partly auto-generated, and the old `connectors/` directory is explicitly in maintenance mode. Those factors prevent a perfect score, but this is a mature, high-craft storage-format project.
This is the TigerGraph ecosystem repository, a large collection of tools, connectors, demos, benchmarks, and tutorials centered around the TigerGraph graph database platform. It is not a single application but an aggregation of community and in-house developed components. The dominant character is application: it includes production-grade ETL connectors (Spark DataSource V2, JDBC driver, Kafka Connect, Hadoop MapReduce), a multi-version GSQL CLI client, a Go-based REST API for remote GSQL management, a Kubernetes operator, and numerous demos showcasing graph analytics (PageRank, community detection, geospatial search, fraud detection, GraphRAG). There are also benchmarking suites (LDBC SNB) and sample data. The codebase exhibits high craftsmanship in the connector and client libraries, with robust retry logic, token management, streaming JSON parsing, and schema inference. However, it suffers from massive code duplication across GSQL client versions, incomplete JDBC driver implementations, hardcoded paths and credentials in demos, and outdated vendored libraries (Leaflet 0.7.7, moment-timezone 2016). Overall, it is a functional but uneven collection; the core connectors are reusable and well-engineered, while many demo scripts are fragile and require manual configuration.