author here. I would actually second you.
My core belief is "it is possible to build true database-like functionalities on top of iceberg", but it is definitely not 'easier' than building them directly in a db (in fact, doing them while keep iceberg-compatible is tricky. yep, that's the cost of being open and general purpose)
Using SQL as catalog is not new (iceberg supports JDBC catalog from the very beginning).
The main difference is to store metadata and stats also directly in SQL databases, which makes perfect sense for smaller scale data. In fact we were doing something similar in https://github.com/Mooncake-Labs/pg_mooncake, metadata are stored in pg tables and only periodically flush to actual formats like iceberg.
DataFile(parquet) is not enough for table with update/delete, (they are part of iceberg "metadata").
for CDC from OLTP use-cases, the pattern involves rapidly marking rows as deleted/ insert new rows and optimizing small files. This is required for minutes-latency replication.
And for second latency replication, it is more involving, you actually need to build layer on top of iceberg to track pk/ apply deletion.
Glab to see more 'postgres-native' full-text search implementation.
Alternative solutions (lucene/ tantivy) are both designed for 'immutable segments' (indexing immutable files), so marrying them with postgres heap table would results in a worse solution.
The focus of mooncake is to be a columnar storage engine, that natively integrate with pg, allowing writing from pg, replicating from pg, and reading by pg using pg_mooncake.
We want people to use other engine to read from mooncake, and here they are effectively stateless engine, that's much easier to manage and avoids all data ETL problems.
Yep what I want say is the line between the two designs is indeed very blur.
Logical replication with mooncake will try to create a columnar version of a postgres heap table, that can be readable within postgres (using pg_mooncake); or outside postgres (similar to peerdb + clickhouse) with other engines like duckdb, StarRocks,Trino and possibly ClickHouse.
But since we can purposely build the columnstore storage engine to have postgres CDC in mind, we can replicate real-time updates/deletes(especially in cases traditional OLAP system won't keep up).
Yea this is indeed a repeated pattern we saw people requesting (filter on many columns) and we are trying to solve with pg_mooncake. If you are interested, feel free to join mooncake-devs.slack.com to chat more about your use case.
Thanks for the comment but you are mixing some terminologies.
The core idea of mooncake is to built upon open columnar format + substitutable vectorized engine, while natively integrate with Postgres.
So it is indeed closer to BigQuery (especially the newer bigquery with iceberg tables) than a 'standard SQL database'. It has all the nice properties of BigQuery (ObjectStore-native, ColumnStore, Vectorized execution...) and scaling is also not impossible.
hydra/pg_duckdb embeds duckdb to query existing data on S3. So it is kind of targeting a completely different use case (someone already prepares and shared a dataset and you just want to query it).
pg_mooncake (&crunchyData) is implementing columnstore tables in postgres, so you can actually use postgres as a data-warehouse (to ingest/ update and run analytics queries)
Good point! Normally for postgres extension it won't be solvable, but for mooncake it is actually not the case!
The core idea of mooncake is to built upon open columnar format + substitutable vectorized engine, while natively integrate with Postgres.
So right now it is using duckdb within postgres to run the query, but we can and we will support ad-hoc using other 'stateless engines' like Athena, StarRocks or even spark to run a big query.
transactions are also managed by postgres as if they are native table, so that you don't need to worry about coordinating commits between postgres and the S3 data.
Interesting enough, the mooncake team was building SingleStore before, and so far it is the best production-ready HTAP system. One lesson I really learned is, people don't want to switch their system-of-record OLTP system.
Spoiler-alert: Mooncake will be supporting HTAP use-cases soon, and it comes with better trade-offs: keep your OLTP postgres tables as is, and mooncake adds analytics capacity to those table on up-to-date data.
Mooncake is built upon open-table formats and substitutable query engines. So it don't need to be just a postgres extension.
PG_mooncake will stay open-source under MIT, for small devs where everything fits in their postgres, we hope everyone to enjoy the !
And we would love to help companies outgrown postgres to transition into the modern stack with postgres + mooncake potentially outside pg + iceberg/delta.
The only datastack iceberg (or lakehouse) will never replace is OLTP systems, for high-concurrency updates optimistic concurrency control & object store is simply a no go.
Iceberg out-of-the-box is "NOT" good at streaming use cases, unlike formats like Hudi or Paimon, the table format does not have the concept of merge/ index. However, the beauty of iceberg is it is very unopinionated, so it is indeed possible to design an engine to stream write to iceberg. As far as I know this is how engines like Upsolver was implemented:
1. Have in-memory buffer to track incoming rows before flushing a version to iceberg (every 10s to a few minutes).
2. Build Indexing structure to write position deletes/ deletion vector instead of equality deletes.
3. The writer will all try to merge small files and optimize the table.
And stay tuned, we at https://www.mooncake.dev/ are working on a solution to mirror a postgres table to iceberg, and keep them always up-to-date.