events

UserService::EventConfig

struct UserService::EventConfig {
    const psibase::AccountNumber service; 

    addIndex(...); // Requests an index. Indexes can improve the performance of queries involving the column. The indexes are subjective and MAY be adjusted by individual nodes. Indexes increase the CPU cost of transactions that create events. Block producers SHOULD use exactly the indexes requested by services to ensure consistent billing.
    sync(...);     // Forwards to event-index::sync
};

The events service maintains indexes for all events..

Queries for events use SQL and are sent to the /sql endpoint with Content-Type: application/sql

There is one table for each type of event, for example, "history.tokens.transferred". Note that double quotes are required because a . is not otherwise allowed in SQL table names.

Each field of the event is a column in the table. Types that are represented in json as a number, string, true, false, or null are represented by an appropriate SQL value and can be compared. Types that do not have a simple representation in SQL are represented by an opaque SQL value. The result of applying any operation to an opaque value other that returning it as a query result is unspecified.

The query result is returned as a JSON array of objects.

Example:

Given an event

void add(uint32_t x, uint32_t y, uint32_t sum);

the query

SELECT * FROM "history.example.add" WHERE sum > 10 ORDER BY x

might return a result that looks like

[{"x":5,"y":7,"sum":12},{"x":6,"y":5,"sum":11}]

UserService::EventConfig::addIndex

void UserService::EventConfig::addIndex(
    psibase::DbId          db,
    psibase::AccountNumber service,
    psibase::MethodNumber  event,
    std::uint8_t           column
);

Requests an index. Indexes can improve the performance of queries involving the column. The indexes are subjective and MAY be adjusted by individual nodes. Indexes increase the CPU cost of transactions that create events. Block producers SHOULD use exactly the indexes requested by services to ensure consistent billing..

UserService::EventConfig::sync

void UserService::EventConfig::sync();

Forwards to event-index::sync.