Function describeQuery

packages/pglite/src/base.ts:331–370

* Describe a query * @param query The query to describe * @returns A description of the result types for the query

(
    query: string,
    options?: QueryOptions,
  )

   * @returns A description of the result types for the query
   */
  async describeQuery(
    query: string,
    options?: QueryOptions,
  ): Promise<DescribeQueryResult> {
    try {
      await this.#execProtocolNoSync(
        serializeProtocol.parse({ text: query, types: options?.paramTypes }),
        options,
      )

      const describeResults = await this.#execProtocolNoSync(
        serializeProtocol.describe({ type: 'S' }),
        options,
      )
      const paramDescription = describeResults.messages.find(
        (msg): msg is ParameterDescriptionMessage =>
          msg.name === 'parameterDescription',
      )
      const resultDescription = describeResults.messages.find(
        (msg): msg is RowDescriptionMessage => msg.name === 'rowDescription',
      )

      const queryParams =
        paramDescription?.dataTypeIDs.map((dataTypeID) => ({
          dataTypeID,
          serializer: this.serializers[dataTypeID],
        })) ?? []

      const resultFields =
        resultDescription?.fields.map((field) => ({
          name: field.name,
          dataTypeID: field.dataTypeID,
          parser: this.parsers[field.dataTypeID],
        })) ?? []

      return { queryParams, resultFields }
    } finally {
      await this.#execProtocolNoSync(serializeProtocol.sync(), options)
    }
  }

  /**
   * Execute a transaction