Re: [sqlite] Join-source issue when using sub '(' join-source ')'

[TAUZIN Mathieu]

Hi,

You're wrong.
I think I've found the bug. 
It is a parser issue.

According to their definition 
(http://sqlite.org/syntaxdiagrams.html#single-source) , Join sources (named 
single-source) are either : 
        * a table or view with an optional alias and/or with an optional index
        * a sub query with an optional alias
        * a sub join (with no alias)

In SQLite parser.y source code we can find on line 496 the grammar rule 
handling those three cases (in the same order)

<snippet line='496'>
...
seltablist(A) ::= stl_prefix(X) nm(Y) dbnm(D) as(Z) indexed_opt(I) on_opt(N) 
using_opt(U). {
  A = sqlite3SrcListAppendFromTerm(pParse,X,&Y,&D,&Z,0,N,U);
  sqlite3SrcListIndexedBy(pParse, A, &I);
}

seltablist(A) ::= stl_prefix(X) LP select(S) RP
                    as(Z) on_opt(N) using_opt(U). {
    A = sqlite3SrcListAppendFromTerm(pParse,X,0,0,&Z,S,N,U);
  }

seltablist(A) ::= stl_prefix(X) LP seltablist(F) RP
                    as(Z) on_opt(N) using_opt(U). {
    if( X==0 && Z.n==0 && N==0 && U==0 ){
      A = F;
    }else{
      Select *pSubquery;
      sqlite3SrcListShiftJoinType(F);
      pSubquery = sqlite3SelectNew(pParse,0,F,0,0,0,0,0,0,0);
      A = sqlite3SrcListAppendFromTerm(pParse,X,0,0,&Z,pSubquery,N,U);
    }
  }
...
</snippet>

Case 1 and 2 are handled properly but as you can see the third definition (wich 
should deal with sub joins) contains mistakes :
        #1 : It allows an as clause after the parenthesis
        #2 : on the right of a join operator (else { ... }) it generates a 
subquery instead of merging F (which is a seltabList, not a sub query) with X 
into A.

Do you still think there is no issue here ?

I wish I could propose a fix but I have no skills in C/yacc.

Hope this will help anyway.

Thanks

-----Message d'origine-----
De : sqlite-users-boun...@sqlite.org [mailto:sqlite-users-boun...@sqlite.org] 
De la part de Nico Williams
Envoyé : lundi 19 mars 2012 16:10
À : General Discussion of SQLite Database
Objet : Re: [sqlite] Join-source issue when using sub '(' join-source ')'

On Mon, Mar 19, 2012 at 10:02 AM, TAUZIN Mathieu <mtau...@cegid.fr> wrote:
> Thanks,
>
> This syntax works but it is not documented... it looks like a short hand for 
> a subquery, interesting !.

Join sources are like sub-queries.  Look at the syntax.

A sub-select specified in the join-source following the FROM clause in a simple 
SELECT statement is handled as if it was a table containing the data returned 
by executing the sub-select statement.  The docs could perhaps be clearer about 
this.  This sentence:

"A sub-select specified in the join-source following the FROM clause in a 
simple SELECT statement is handled as if it was a table containing the data 
returned by executing the sub-select statement. "

does hint at this, but maybe that's just because I think of <single-source> as 
a sort of sub-select.

Nico
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