Default to omni

[levkk]

Omnisharded tables

We now treat all tables as omnisharded unless they are configured in pgdog.toml. This makes configuration a lot easier. To make this work we load the Postgres schema from system catalogs on boot and inspect it for tables that match the config for each query. This is quick, since the tables (and their columns) are organized in a HashMap.

Schema inference

We now load schema from Postgres on boot and inspect it for sharding keys. To make this work, Postgres needs to be available when PgDog is started.

Migrations

When adding/changing sharded tables, make sure to run RELOAD (or RECONNECT) to reload the schema, otherwise a SELECT against the new table will default to omni, not sharded, for queries that don't provide the sharding key.

Unique ID generation

This has been removed in #727

Added pgdog.unique_id() to Postgres itself (via setup CLI command), so it's now possible to add it as a default to a table, e.g.:

CREATE TABLE omni (
    id BIGINT NOT NULL DEFAULT pgdog.unique_id(),
    value TEXT,
);

How this works:

1. Configure shards in pgdog.toml
2. Run pgdog setup to create the function and its dependencies. This will create a schema called pgdog on all shards and the pl/PgSQL functions will be added to it.

Warning

Don't use the Postgres unique ID function to generate sharding keys! They won't match the shard they are generated on. Make sure to call it explicitly in the query so PgDog executes it instead.

[codecov]

Codecov Report

❌ Patch coverage is 94.32773% with 27 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
pgdog/src/frontend/router/parser/statement.rs	69.69%	10 Missing ⚠️
pgdog/src/backend/schema/mod.rs	96.93%	5 Missing ⚠️
pgdog/src/backend/pool/shard/mod.rs	78.57%	3 Missing ⚠️
pgdog/src/backend/schema/relation.rs	40.00%	3 Missing ⚠️
pgdog/src/backend/pool/cluster.rs	98.67%	2 Missing ⚠️
...og/src/frontend/client/query_engine/route_query.rs	83.33%	2 Missing ⚠️
pgdog/src/frontend/router/parser/query/select.rs	96.42%	2 Missing ⚠️

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