@sqb/connect/client/cursor-stream.js

Multi-dialect database connection framework written with TypeScript

import _debug from 'debug';
import { Readable } from 'stream';
const inspect = Symbol.for('nodejs.util.inspect.custom');
const debug = _debug('sqb:cursorstream');
export class CursorStream extends Readable {
    _cursor;
    _objectMode;
    _limit;
    _rowNum = -1;
    _eof = false;
    constructor(cursor, options) {
        super(options);
        this._cursor = cursor;
        this._objectMode = options?.objectMode;
        this._limit = options?.limit || Number.MAX_SAFE_INTEGER;
        this.on('end', () => {
            this.close().catch(() => false);
        });
        cursor.once('close', () => this.emit('close'));
        cursor.on('error', err => this.emit('error', err));
    }
    /**
     * Returns if stream is closed.
     */
    get isClosed() {
        return this._cursor.isClosed;
    }
    /**
     * Closes stream and releases the cursor
     */
    close() {
        this.pause();
        this.unpipe();
        return this._cursor.close();
    }
    toString() {
        return '[object ' + Object.getPrototypeOf(this).constructor.name + ']';
    }
    [inspect]() {
        return this.toString();
    }
    _read() {
        if (this._rowNum >= this._limit) {
            this.pause();
            this.unpipe();
            this.emit('end');
            return;
        }
        this._cursor
            .next()
            .then(row => {
            if (this._eof)
                return this.push(null);
            let buf = '';
            if (this._rowNum < 0) {
                this._rowNum = 0;
                if (!this._objectMode)
                    buf += '[';
            }
            if (!row) {
                this._eof = true;
                if (!this._objectMode) {
                    buf += ']';
                    this.push(buf);
                }
                else
                    this.push(null);
                return;
            }
            this._rowNum++;
            if (this._objectMode)
                this.push(row);
            else {
                if (this._rowNum > 1)
                    buf += ',';
                this.push(buf + JSON.stringify(row));
            }
        })
            .catch(err => {
            /* istanbul ignore next */
            if (typeof this.destroy == 'function')
                this.destroy(err);
            else
                this.emit('error', err);
            this.close().catch(() => 0);
        });
    }
    emit(event, ...args) {
        try {
            if (event === 'error' && !this.listenerCount('error'))
                return false;
            return super.emit(event, ...args);
        }
        catch (ignored) {
            debug('emit-error', ignored);
            return false;
        }
    }
}