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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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47
src/backend/parser/analyze.c
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@@ -1809,6 +1809,33 @@ transformSetOperationStmt(ParseState *pstate, SelectStmt *stmt)
return qry;
}
/*
* Make a SortGroupClause node for a SetOperationStmt's groupClauses
*/
SortGroupClause *
makeSortGroupClauseForSetOp(Oid rescoltype)
{
SortGroupClause *grpcl = makeNode(SortGroupClause);
Oid sortop;
Oid eqop;
bool hashable;
/* determine the eqop and optional sortop */
get_sort_group_operators(rescoltype,
false, true, false,
&sortop, &eqop, NULL,
&hashable);
/* we don't have a tlist yet, so can't assign sortgrouprefs */
grpcl->tleSortGroupRef = 0;
grpcl->eqop = eqop;
grpcl->sortop = sortop;
grpcl->nulls_first = false; /* OK with or without sortop */
grpcl->hashable = hashable;
return grpcl;
}
/*
* transformSetOperationTree
* Recursively transform leaves and internal nodes of a set-op tree
@@ -2109,31 +2136,15 @@ transformSetOperationTree(ParseState *pstate, SelectStmt *stmt,
*/
if (op->op != SETOP_UNION || !op->all)
{
SortGroupClause *grpcl = makeNode(SortGroupClause);
Oid sortop;
Oid eqop;
bool hashable;
ParseCallbackState pcbstate;
setup_parser_errposition_callback(&pcbstate, pstate,
bestlocation);
/* determine the eqop and optional sortop */
get_sort_group_operators(rescoltype,
false, true, false,
&sortop, &eqop, NULL,
&hashable);
op->groupClauses = lappend(op->groupClauses,
makeSortGroupClauseForSetOp(rescoltype));
cancel_parser_errposition_callback(&pcbstate);
/* we don't have a tlist yet, so can't assign sortgrouprefs */
grpcl->tleSortGroupRef = 0;
grpcl->eqop = eqop;
grpcl->sortop = sortop;
grpcl->nulls_first = false; /* OK with or without sortop */
grpcl->hashable = hashable;
op->groupClauses = lappend(op->groupClauses, grpcl);
}
/*