Types

ElectricSQL syncs data between Postgres and SQLite.

To do this, we map between Postgres data types and SQLite data types. In addition, we validate local writes to ensure that the values written into the local database will successfully replicate into Postgres.

As a result, we support a limited set of validated Postgres data types. If you try to electrify a table which contains unsupported types or constraints, this will fail. The same applies to altering an electrified table.

Primary keys

Tables must have an explicit primary key. Primary keys must be unique and immutable.

ElectricSQL does not support sequential autoincrementing integer IDs. You must use globally unique primary key identifiers. Typically this means binary UUIDs.

You are responsible for ensuring the uniqueness of your primary keys. If you somehow concurrently create two rows with the same primary key this will cause an integrity violation when the rows are synced.

Supported data types

Work in progress

We are actively working on building out data type support. If you need a type we don't yet support, please let us know on Discord.

Numeric:

• smallint / int2
• integer / int / int4
• bigint / int8
• real / float4
• double precision / float8

Strings:

• character varying / varchar (without length specifier)
• text

Date and time:

• date
• time (without precision specifier)
• timestamp, timestamptz (without precision specifier)

Other:

• boolean
• enum (any user-defined enumerated type)
• bytea / blob (see supported SQLite drivers)
• jsonb
• uuid

JSON support

Electric defaults to a Last-Writer-Wins strategy. For JSON this is across the whole document - updating one attribute in the document counts as the document as a whole being updated. This means that conflicting updates from multiple clients are not merged together, the full state of the last writer will be stored.

In future we plan to support more fine grained merge strategies for JSON data.

BYTEA support

ElectricSQL supports bytea data but not all SQLite drivers are capable of reading/writing blobs - see table below:

wa-sqlite	better-sqlite3	expo-sqlite	expo-sqlite/next	op-sqlite
✅︎	✅︎	❌	✅︎	✅︎

Note that reading/writing empty byte arrays might produce different results depending on the driver.

Enum type caveats

Each enum label (aka enum value) must match the regular expression ^[a-zA-Z][a-zA-Z0-9_]*$. In other words, it should look like a valid identifier.

We don't yet support modifying an enum type (i.e. ALTER TYPE .. ADD VALUE) if it's used by a column in an electrified table.

It's not yet possible to alter an electrified table and add a new column of an enum type to it.

Both limitations will be removed in a future release.