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[MySQL]: optimize result set streaming from iterator() #4126

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[MySQL]: optimize result set streaming from iterator() #4126

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1c8515c
fix(mysql): optimize result set streaming
reecefenwick Feb 16, 2025
1f577ac
fix(mysql): do more in a try/catch
reecefenwick Feb 16, 2025
745253b
fix(mysql): restore invariant checks
reecefenwick Feb 16, 2025
bc8f583
fix(mysql): remove redundant invariant checks now that Promise.race i…
reecefenwick Feb 17, 2025
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42 changes: 12 additions & 30 deletions drizzle-orm/src/mysql2/session.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,6 @@ import type {
ResultSetHeader,
RowDataPacket,
} from 'mysql2/promise';
import { once } from 'node:events';
import { Column } from '~/column.ts';
import { entityKind, is } from '~/entity.ts';
import type { Logger } from '~/logger.ts';
Expand Down Expand Up @@ -137,43 +136,26 @@ export class MySql2PreparedQuery<T extends MySqlPreparedQueryConfig> extends MyS
}).connection;

const { fields, query, rawQuery, joinsNotNullableMap, client, customResultMapper } = this;
const hasRowsMapper = Boolean(fields || customResultMapper);
const driverQuery = hasRowsMapper ? conn.query(query, params) : conn.query(rawQuery, params);

const stream = driverQuery.stream();

function dataListener() {
stream.pause();
}

stream.on('data', dataListener);

try {
const onEnd = once(stream, 'end');
const onError = once(stream, 'error');
const hasRowsMapper = Boolean(fields || customResultMapper);
const driverQuery = hasRowsMapper ? conn.query(query, params) : conn.query(rawQuery, params);

while (true) {
stream.resume();
const row = await Promise.race([onEnd, onError, new Promise((resolve) => stream.once('data', resolve))]);
if (row === undefined || (Array.isArray(row) && row.length === 0)) {
break;
} else if (row instanceof Error) { // eslint-disable-line no-instanceof/no-instanceof
throw row;
} else {
if (hasRowsMapper) {
if (customResultMapper) {
const mappedRow = customResultMapper([row as unknown[]]);
yield (Array.isArray(mappedRow) ? mappedRow[0] : mappedRow);
} else {
yield mapResultRow(fields!, row as unknown[], joinsNotNullableMap);
}
const stream = driverQuery.stream();

for await (const row of stream) {
if (hasRowsMapper) {
if (customResultMapper) {
const mappedRow = customResultMapper([row as unknown[]]);
yield (Array.isArray(mappedRow) ? mappedRow[0] : mappedRow);
} else {
yield row as T['execute'];
yield mapResultRow(fields!, row as unknown[], joinsNotNullableMap);
}
} else {
yield row as T['execute'];
}
}
} finally {
stream.off('data', dataListener);
if (isPool(client)) {
conn.end();
}
Expand Down