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SEARCH and CYCLE clauses

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This adds the SQL standard feature that adds the SEARCH and CYCLE
clauses to recursive queries to be able to do produce breadth- or
depth-first search orders and detect cycles.  These clauses can be
rewritten into queries using existing syntax, and that is what this
patch does in the rewriter.

Reviewed-by: Vik Fearing <vik@postgresfriends.org>
Reviewed-by: Pavel Stehule <pavel.stehule@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/db80ceee-6f97-9b4a-8ee8-3ba0c58e5be2@2ndquadrant.com
This commit is contained in:
Peter Eisentraut
2021-02-01 13:54:59 +01:00
parent bb513b364b
commit 3696a600e2
28 changed files with 2301 additions and 33 deletions
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18
src/backend/rewrite/rewriteHandler.c
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@@ -38,6 +38,7 @@
#include "rewrite/rewriteDefine.h"
#include "rewrite/rewriteHandler.h"
#include "rewrite/rewriteManip.h"
#include "rewrite/rewriteSearchCycle.h"
#include "rewrite/rowsecurity.h"
#include "utils/builtins.h"
#include "utils/lsyscache.h"
@@ -2079,6 +2080,23 @@ fireRIRrules(Query *parsetree, List *activeRIRs)
int rt_index;
ListCell *lc;
/*
* Expand SEARCH and CYCLE clauses in CTEs.
*
* This is just a convenient place to do this, since we are already
* looking at each Query.
*/
foreach(lc, parsetree->cteList)
{
CommonTableExpr *cte = lfirst_node(CommonTableExpr, lc);
if (cte->search_clause || cte->cycle_clause)
{
cte = rewriteSearchAndCycle(cte);
lfirst(lc) = cte;
}
}
/*
* don't try to convert this into a foreach loop, because rtable list can
* get changed each time through...