On 10/03/2021 15:42, Adriano dos Santos Fernandes wrote: > On 10/03/2021 05:30, Dmitry Yemanov wrote: >> 06.03.2021 14:53, Mark Rotteveel wrote: >> >>> Now I wonder, what would be necessary to introduce this alternative? >>> Would this be a matter of adding the right alternative and adding the >>> order by and offset/fetch info to the RseNode returned by the query >>> expression, or would more be needed? >> >> I'm afraid it's not gonna work. >> >> RseNode has dsqlOrder, but it's not used directly inside the parser >> (query_spec does not define ordering itself), so at the first glance it >> looks like it could be safely assigned in the new parser rules. However, >> implementation inside pass1.cpp moves the order node from SelectExprNode >> into underlying RseNode::dsqlOrder, so it might undo your work at the >> parser level in cases like this: >> >> ( select ... order by A ) order by B >> >> in this particular example it's OK, as nobody would see the ordering by >> A anyway. But it FIRST/ROWS/FETCH is applied too, ordering by A becomes >> a requirement. >> >> As for OFFSET/FETCH, things are even trickier. RseNode supports >> dsqlFirst/dsqlSkip, but they're used for legacy FIRST/SKIP inside >> query_spec. What to do in these cases: >> >> (select first 10 ...) fetch first 5 rows >> ( select ... fetch first 10 rows ) fetch first 5 rows >> >> where "10" may be replaced with "5". This looks safer than for the ORDER >> BY case but I'm not sure I can see all the subsequences. >> >> Perhaps query_term should return SelectExprNode* and the new parser >> rules define new SelectExprNode with querySpec/orderClause/rowsClause >> set up based on select_expr_body/order_clause_opt/rows_clause. But I'm >> pretty sure some code places are not prepared to see query_term as >> SelectExprNode*. >> > > I did some tests and attached is a patch (v3). > > It introduces conflicts which I didn't looked yet.
I see now that the introduced reduce/reduce conflict comes from: insert into table (column_list) (select insert into table (column_list) values ( insert into table (select Which are valid from the standard POV. Adriano Firebird-Devel mailing list, web interface at https://lists.sourceforge.net/lists/listinfo/firebird-devel
