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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/utils/adt/ruleutils.c
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@ -5168,6 +5168,53 @@ get_with_clause(Query *query, deparse_context *context)
if (PRETTY_INDENT(context))
appendContextKeyword(context, "", 0, 0, 0);
appendStringInfoChar(buf, ')');
if (cte->search_clause)
{
bool first = true;
ListCell *lc;
appendStringInfo(buf, " SEARCH %s FIRST BY ",
cte->search_clause->search_breadth_first ? "BREADTH" : "DEPTH");
foreach(lc, cte->search_clause->search_col_list)
{
if (first)
first = false;
else
appendStringInfoString(buf, ", ");
appendStringInfoString(buf,
quote_identifier(strVal(lfirst(lc))));
}
appendStringInfo(buf, " SET %s", quote_identifier(cte->search_clause->search_seq_column));
}
if (cte->cycle_clause)
{
bool first = true;
ListCell *lc;
appendStringInfoString(buf, " CYCLE ");
foreach(lc, cte->cycle_clause->cycle_col_list)
{
if (first)
first = false;
else
appendStringInfoString(buf, ", ");
appendStringInfoString(buf,
quote_identifier(strVal(lfirst(lc))));
}
appendStringInfo(buf, " SET %s", quote_identifier(cte->cycle_clause->cycle_mark_column));
appendStringInfoString(buf, " TO ");
get_rule_expr(cte->cycle_clause->cycle_mark_value, context, false);
appendStringInfoString(buf, " DEFAULT ");
get_rule_expr(cte->cycle_clause->cycle_mark_default, context, false);
appendStringInfo(buf, " USING %s", quote_identifier(cte->cycle_clause->cycle_path_column));
}
sep = ", ";
}