AdamProut

I'm curious why the test needed so many router hosts:

512 shards, each with one Postgres primary each on an r8g.16xlarge

480 Neki routers, each on its own 8xlarge instance

That's ~250K queries/sec per router which seems lowish for this type of workload? The routers won't be doing very much (parse query, route it to proper shard?).

yeah, this is a definitely a "best case" workload for a sharded database. Single row reads on the key used to shard with no hotspots (no shard to shard network traffic at all).

I'll admit to not reading your code. It's hard to keep up with all the different databases launched in the last decade.

I have doubts that a global readwrite lock around a hashtable makes for a good general purpose storage system.

what kind of maintenance?

I think one of the maybe less talked about benefits of distributed SQL is support for nearly transparent rolling upgrades of the database with very little impact to a running workload. Spanner is best in class at this.

The intro section is a good summary of why distributed SQL databases (Spanner, roach, Yugabyte, TiDB) haven't taken off in the market in the same way as say distributed data warehouses have (Snowflake, Databricks, FabricDW, Clickhouse, etc.).

I would add a few other things to the list of scaling problems. Some SQL features are hard to scale out (auto_increment/serial columns, unique secondary keys, foreign keys, etc.). Some SQL query operators are hard to scale out for OLTP queries that want low latency and high throughput (DISTINCT, LIMIT/TOP-N, non-collocated joins). I take it SpacetimeDB is a nosql database, so these problems are less important to them?

As to how spacetimedb plans to scale out, I didn't follow it fully. It's hard to take the spacetimedb folks seriously (see: https://strn.cat/posts/spacetime/).

Agents should be driving up the quality of software if we focus them on finding and fixing bugs.

Very cool! pg_duckdb itself is missing fully integrated storage - it can query data stored externally (say in S3) in delta/iceberg formats, but it can't write out data in those formats via transactional writes to PG tables (insert\update\deletes). pg_mooncacke is one neat way of solving that problem. It lets you have a columnstore table in Postgres that can do both reads and writes as if it's any other PG table and have the storage format be an open format like delta/iceberg/etc with that data persisted to blob store (like most cloud DWs would do anyways).

Had a similar thought. Azure Postgres has something similar to pg_parquet (pg_azure_storage), but we're looking into replacing it with pg_duckdb assuming the extension continues to mature.

It would be great if the Postgres community could get behind one good opensource extension for the various columnstore data use cases (querying data stored in an open columnstore format - delta, iceberg, etc. being one of them). pg_duckdb seems to have the best chance at being the goto extension for this.

Checksums can detect a torn page, but not always repair them. It's likely a good part of the database page is gone (i.e., an amount of data that matches the disk / file system atomic write unit size is probably missing). Torn page writes are a pretty common scenario too, so databases need to be able to fully recover from them - not just detect them and report a corruption (ie., just pull the power plug from the machine during a heavy write workload and you're likely to get one - it doesn't require a solar ray to flip a bit :) ).

Maybe good to mention torn pages somewhere too? Both MySQL and Postgres jump through some hoops to both detect them and repair them [1][2]. So, even the scenario in the post where fsync is used to harden writes, the database still needs to handle torn pages (or requires using a file system \ storage that guarantees atomic page writes at the page size the database is using as several managed\cloud databases do).

[1] https://wiki.postgresql.org/wiki/Full_page_writes [2] https://dev.mysql.com/doc/refman/8.0/en/innodb-doublewrite-b...

I'm not sure why you're getting downvoted. I think the pressure to appease Gartner usually starts when companies bring in CEOs whose primary background is enterprise sales. They tend to over value magic quadrant positioning (in my view).

Based on the writings of 2 Turing awards winners for work on databases; No MongoDB doesn't have ACID transactions.

Control theory is also used by databases (probably not as often as it should be). It's great for "self tuning" [1], for example tuning the various cache sizes a database has to maximize throughput under changing workload conditions. Its definitely worth spending the time to understand PID controllers if your an engineer working on databases.

[1] https://www.vldb.org/conf/2006/p1081-storm.pdf

RE: "Distributed SQL offers elasticity (no downtime resize"). I'm not sure this is as much of an advantage of distributed databases vs single host databases anymore. Some of the tech to move virtual machines between machines quickly (without dropping TCP connections) is pretty neat. Neon has a blog post about it here[1]. Aurora Serverless V2 does the same thing (but I can't find a detailed technical blog post talking about how it works). Your still limited by "one big host" but its no longer as big of a deal to scale your compute up/down within that limit.

[1] https://neon.tech/blog/scaling-serverless-postgres

Databricks has kept their Photon[1][2] query engine for Spark closed sourced thus far. Unless EMR has made equivalent changes to the Spark runtime they use Databricks should be much faster. Photon brings the standard vectorized execution techniques used in SQL data warehouses for many years to Spark.

[1] https://docs.databricks.com/en/clusters/photon.html [2] https://dl.acm.org/doi/10.1145/3514221.3526054

yeah, that is part of the trade off. Using an ephemeral SSD (for a database) means the database needs to have another means of making the data durable (replication, storing data in S3, etc.).

There are AWS instance types (I3en) with large and very fast SSDs (many times higher IOPS then EBS).

Its a popular design for SQL Data warehouses. I think almost all of them (snowflake, redshift, etc.) store cold data in S3 and hot data on local disk[1][2].

It works well if the data is stored as immutable files (i.e., A log structure merge tree) or is not index at all (classical columnstores). S3 doesn't provide an efficient way to update a file.

[1] https://dl.acm.org/doi/10.1145/2882903.2903741 (snowflake SIGMOD paper) [2] https://dl.acm.org/doi/10.1145/3514221.3526055 (singlestore SIGMOD paper)

Yeah for workloads with any long running write transactions a single writer design is a pretty big limitation. Say some long running data load (or a big bulk deletion) running along with some faster high throughput key value writes - the big data load would block all the faster key-value writes when it runs.

No "mainstream" database I'm aware of has a global single writer design.

This may depend on if your use case is only vector search in isolation (ANN lookups). In this scenario PG Vector is potentially not the best option (https://ann-benchmarks.com/)

That said, using PG Vector (or using other SQL databases with vector search support.. many have this capability) will let you do both ANN and your usual SQL filtering and joining (or full text, or.. etc) to produce more hand tuned results to a query. This is something the specialized vector databases don't have much support for.

Yep, SingleStoreDB (formerly MemSQL) is not open source (probably never will be), but it does have many paying customers who have had workloads in production for over a decade at this point.

Also, isn't taking a bet on a very recently launched database as a service based around an open source database also pretty risky? Say for example the very recently launched Clickhouse Inc. service (which your a co-founder of?).

Most SQL Analytical databases don't discourage joins (think BigQuery, Redshift, Snowflake, etc.) and all of them are columnstores. I think discouraging joins is something very specific to Clickhouse, Druid, Pinot and others that have very limited support for joins.

Yep, for writes network bandwidth usage is independent of separation of storage of compute in some sense. Any database that provides high availability is writing over the network somewhere before it acks a transaction committed. It matters who is on the other end of that network write though. Take the typical Cloud DW (i.e., Snowflake) design of forcing writes to the blob storage (shared remote disks) before commit. That is a much higher latency write then what a high performance transaction log replication protocol will do to replicate a write to another host.

There are hybrid designs for separation of storage and compute that are aimed at mixed workloads[1]. They avoid writes to remote storage on transaction commit (i.e., act like a shared nothing databases for commits, but still push data asynchronously to a shared remote disk that can be used for scale up/point in time restores/branching).

[1] https://www.singlestore.com/blog/separating-storage-and-comp...

(disclosure: SingleStoreDB CTO)

Columnstores can do row level access by trading off a bit in terms of compression. If you organize the columnstore files as an LSM tree and use incremental compression schemes (so you don't have to compress too many more rows then the one your after) it can get close to the performance of a B-Tree for point reads - it depends on the specific table schema.

[1] https://dl.acm.org/doi/abs/10.1145/3514221.3526055

I read the article. And yes, this was probably a mistake to engage with you on it.

Yandex N.V. (A dutch holding company of Yandex Russia) is listed as an investor of Clickhouse Inc. This is all I'm stating.

Because half truths like your statements bother me? Yandex is a large investor in clickhouse Inc. (at last as far as public record shows). Have they forced Yandex to divest their holdings?

Yandex (Google of Russia) is a large share holder of Clickhouse Inc[1]. Yes, this maybe a European Yandex subsidiary.. I really don't care to dig, but I think its dishonest to say the company doesn't have Russian backers. Has Clickhouse Inc forced Yandex to divest their large ownership stake?

[1] https://www.crunchbase.com/organization/clickhouse/company_f...

Almost no one does "official" TPC results these days (maybe other then Oracle and some of the Chinese vendors).

Most other cloud DWs have public TPC-H or TPC-DS results that are easily googlable. Clickhouse is missing for a reason...

  - https://research.gigaom.com/report/data-warehouse-cloud-benchmark/
  - https://www.databricks.com/blog/2021/11/02/databricks-sets-official-data-warehousing-performance-record.html
  - https://celerdata.com/blog/starrocks-queries-outperform-clickhouse-apache-druid-and-trino
  - https://aws.amazon.com/blogs/big-data/amazon-redshift-continues-its-price-performance-leadership/

Our results are here: https://www.singlestore.com/blog/tpc-benchmarking-results/