TypeORM 0.3

[webjay]

This works for TypeORM 0.3:

// Modified for TypeORM 0.3 from @zamarawka/typeorm-explain

import { ObjectLiteral, QueryBuilder } from 'typeorm';

export enum ExplainFormat {
  JSON = 'json',
  TEXT = 'text',
  XML = 'xml',
  YAML = 'yaml',
}

type PostgresExplainParameters = {
  analyze?: boolean;
  verbose?: boolean;
  costs?: boolean;
  buffers?: boolean;
  timing?: boolean;
};

type ExplainParameters = PostgresExplainParameters | undefined;

type ExplainBuilder = (
  query: string,
  explainParameters: ExplainParameters,
  format: ExplainFormat
) => string;

const explainers: { [key: string]: ExplainBuilder } = {
  postgres(
    query: string,
    explainParameters: PostgresExplainParameters = {
      analyze: true,
      verbose: true,
      buffers: true,
    },
    format: ExplainFormat
  ) {
    const boolParameters = Object.entries(explainParameters)
      .filter((argument): argument is [string, boolean] => typeof argument[1] === 'boolean')
      .map(([key, value]) => `${key} ${value}`);

    const explainParametersString = [...boolParameters, `FORMAT ${format}`]
      .join(', ')
      .toUpperCase();

    return `EXPLAIN (${explainParametersString}) ${query}`;
  },
};

const explain = <T extends ObjectLiteral>(
  qb: QueryBuilder<T>,
  format = ExplainFormat.TEXT,
  explainParameters?: ExplainParameters
): Promise<unknown> => {
  const { connection } = qb.clone();
  const explainBuilder = explainers[connection.driver.options.type] as ExplainBuilder | undefined;
  if (explainBuilder === undefined) throw new Error('Unsupported connection driver');
  const [query, queryParameters] = qb.getQueryAndParameters();
  const queryExplain = explainBuilder(query, explainParameters, format);

  return connection.query(queryExplain, queryParameters);
};

// eslint-disable-next-line import/no-default-export
export default explain;

[david-vendel]

Thanks, this works, I'll add the usage for others:

import explain from 'src/lib/explain';
...
const queryExplained = await explain(query);
console.log('queryExplained', queryExplained);

Where the content of 'src/lib/explain'; is the code you quoted above and query is a standard TypeORM query created with queryBuilder.