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Version: LOC v0.9 (legacy)

Database Query

For executing a select/action query given by another logic and write the query result (if any) to session storage.

Logic typeInputOutput
GenericSession variable sql
  • Session variable db_resp (type: QueryResults for select queries or null for action queries)
  • Session variable db_query_status indicates if the action was successful (boolean)
  • Session variable db_error indicates any error occurred (null if none)
note

For this logic to be reusable, the sql session should be provided by one of the previous logic and must conform the following type:

{
    configName: string;  // database configuration reference name
    statement: string;  // SQL statement, for example, "select * from table;"
    params: any[];  // parameters (as an array) in the SQL prepared statement
}

The logic will execute a select query if the statement contains the select keyword (which will return a response object), or execute an action query for else.

The logic will not throw an error to halt the data process. Instead the error would be passed to session variable db_error

warning

This logic requires a database configuration. See the tutorial for how to create one and add it to a logic in a data process.

database-query.js
import {
    DatabaseAgent,
    LoggingAgent,
    SessionStorageAgent,
} from "@fstnetwork/loc-logic-sdk";

export async function run(ctx) {
    // read sql object from session
    const sql = await SessionStorageAgent.get("sql");

    /* or comment out the line above and replace sql object with the following declaration:
    const sql = {
        configName: "db config name",
        statement: "select * from table where col_1 = ? and col_2 = ?;",
        params: ["value_1", "value_2"],
    }
    */

    // skip logic if sql session variable does not exist (is null)
    if (!sql) return;

    // throws an error if fields in sql are missing
    if (
        !(typeof sql == "object") ||
        !("configName" in sql) ||
        !("statement" in sql) ||
        !("params" in sql)
    )
        throw new Error("sql is not an object or has missing fields!");

    // log sql object
    LoggingAgent.info({ sql: sql });

    let dbClient = null;
    let resp = null;
    let db_query_status = "error";
    let db_error = null;

    try {
        // aquire database client
        dbClient = await DatabaseAgent.acquire(sql.configName);
        LoggingAgent.info("database client acquired");
        LoggingAgent.info({
            dataSourceId: dbClient.uid.dataSourceId,
            connectionId: dbClient.uid.connectionId,
        });

        // run select or action query
        if (sql.statement.toLowerCase().includes("select")) {
            resp = await dbClient?.query(sql.statement, sql.params);
        } else {
            await dbClient?.execute(sql.statement, sql.params);
        }

        db_query_status = "ok";
    } catch (e) {
        db_error = {
            error: true,
            errorMessage: `database query error: ${e.message}`,
            stack: e.stack,
            taskKey: ctx.task.taskKey,
        };
        LoggingAgent.error(db_error);
    } finally {
        // release database connection
        await dbClient?.release();
    }

    // log query result and db action status
    LoggingAgent.info({ db_resp: resp });
    LoggingAgent.info(`db_action_status: ${db_action_status}`);

    // write query result, query status and error into session storage
    await SessionStorageAgent.putJson("db_resp", resp);
    await SessionStorageAgent.putString("db_query_status", db_query_status);
    await SessionStorageAgent.putJson("db_error", db_error);
}

export async function handleError(ctx, error) {
    // error logging
    LoggingAgent.error({
        error: true,
        errorMessage: error.message,
        stack: error.stack,
        taskKey: ctx.task.taskKey,
    });
}