Обсуждение: What type of Compiler to SQL? Memory-Image (Load-and-Go) Format?

On Fri, May  5, 2023 at 01:00:37AM +0000, Wen Yi wrote:
> Hi team,
> I am a newbie to the postgres.
> When I am studying the compiler,the text book tell me there is there type of
> compiler.
> 
>  1. Assembly Language Format
>  2. Relocatable Binary Format
>  3. Memory-Image (Load-and-Go) Format
> 
> I check the postgres's sql compiler, and it's achieved by lex & yacc.
> So What type of Compiler to SQL? Is Memory-Image (Load-and-Go) Format ?

Lex and yacc load command-specific structures, or a Query structure for
SELECT, INSERT, UPDATE, DELETE, MERGE.

The Query structure is converted into a Plan which is executed by the
executor.  It is not compiled into assembly language.  See this:

    https://www.postgresql.org/developer/backend/

A
-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  Embrace your flaws.  They make you human, rather than perfect,
  which you will never be.

On Thu, May  4, 2023 at 09:16:20PM -0400, Bruce Momjian wrote:
> Lex and yacc load command-specific structures, or a Query structure for
> SELECT, INSERT, UPDATE, DELETE, MERGE.
> 
> The Query structure is converted into a Plan which is executed by the
> executor.  It is not compiled into assembly language.  See this:
> 
>     https://www.postgresql.org/developer/backend/

Oh, this might help too:

    https://momjian.us/main/writings/pgsql/internalpics.pdf

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  Embrace your flaws.  They make you human, rather than perfect,
  which you will never be.

> On May 4, 2023, at 18:00, Wen Yi <chuxuec@outlook.com> wrote:
>
> Hi team,
> I am a newbie to the postgres.
> When I am studying the compiler,the text book tell me there is there type of compiler.
>     • Assembly Language Format
>     • Relocatable Binary Format
>     • Memory-Image (Load-and-Go) Format
> I check the postgres's sql compiler, and it's achieved by lex & yacc.
> So What type of Compiler to SQL? Is Memory-Image (Load-and-Go) Format ?

Hi,

Those aren't really "types of compilers."  They are different binary output formats that a compiler can generate.

PostgreSQL does not have an "SQL compiler" as such.  (It does have Just-in-Time compilation for some operations, but
that'salmost certainly not what you are looking for.)  It's an interpreter, in that it transforms the input language to
aninternal representation and then uses that for its execution, rather than reducing it all the way to machine
language.