Message-ID: <7a3a478be2a16465ac93ba01b13e1081568cbbd9.camel@cybertec.at>
Subject: Re: psql's FETCH_COUNT (cursor) is not being respected for CTEs
From: Laurenz Albe <laurenz.albe@cybertec.at>
To: Daniel Verite <daniel@manitou-mail.org>
Cc: PostgreSQL Hackers <pgsql-hackers@postgresql.org>, Tom Lane
	 <tgl@sss.pgh.pa.us>, Robert Haas <robertmhaas@gmail.com>, Jakub Wartak
	 <jakub.wartak@enterprisedb.com>
Date: Fri, 29 Mar 2024 14:07:06 +0100
In-Reply-To: <b3609dbf-5880-4ead-bb83-c1ccea7c879d@manitou-mail.org>
References: <b3609dbf-5880-4ead-bb83-c1ccea7c879d@manitou-mail.org>
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Precedence: bulk

On Tue, 2024-01-30 at 15:29 +0100, Daniel Verite wrote:
> PFA a rebased version.

I had a look at patch 0001 (0002 will follow).

> - <sect1 id=3D"libpq-single-row-mode">
> -  <title>Retrieving Query Results Row-by-Row</title>
> + <sect1 id=3D"libpq-chunked-results-modes">
> +  <title>Retrieving Query Results by chunks</title>

That should be "in chunks".

> +    <para>
> +   <variablelist>
> +    <varlistentry id=3D"libpq-PQsetChunkedRowsMode">
> +      <term><function>PQsetChunkedRowsMode</function>
> +        <indexterm><primary>PQsetChunkedRowsMode</primary></indexterm></=
term>
> +     <listitem>
> +      <para>
> +       Select the mode retrieving results in chunks for the currently-ex=
ecuting query.

That is questionable English.  How about

  Select to receive the results for the currently-executing query in chunks=
.

> +       This function is similar to <xref linkend=3D"libpq-PQsetSingleRow=
Mode"/>,
> +       except that it can retrieve a user-specified number of rows
> +       per call to <xref linkend=3D"libpq-PQgetResult"/>, instead of a s=
ingle row.

The "user-specified number" is "maxRows".  So a better wording would be:

  ... except that it can retrieve <replaceable>maxRows</replaceable> rows
  per call to <xref linkend=3D"libpq-PQgetResult"/> instead of a single row=
.

> -    error.  But in single-row mode, those rows will have already been
> +    error.  But in single-row or chunked modes, those rows will have alr=
eady been

I'd say it should be "in *the* single-row or chunk modes".

> --- a/src/interfaces/libpq/fe-exec.c
> +++ b/src/interfaces/libpq/fe-exec.c
> @@ -41,7 +41,8 @@ char     *const pgresStatus[] =3D {
>     "PGRES_COPY_BOTH",
>     "PGRES_SINGLE_TUPLE",
>     "PGRES_PIPELINE_SYNC",
> -   "PGRES_PIPELINE_ABORTED"
> +   "PGRES_PIPELINE_ABORTED",
> +   "PGRES_TUPLES_CHUNK"
>  };

I think that PGRES_SINGLE_TUPLE and PGRES_TUPLES_CHUNK should be next to ea=
ch
other, but that's no big thing.
The same applies to the change in src/interfaces/libpq/libpq-fe.h

I understand that we need to keep the single-row mode for compatibility
reasons.  But I think that under the hood, "single-row mode" should be the
same as "chunk mode with chunk size one".
That should save some code repetition.

Yours,
Laurenz Albe