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/*-------------------------------------------------------------------------
*
* subselect.c
* incremental view maintenance extension
* Routines for CTE support.
*
* Portions Copyright (c) 2023, IVM Development Group
* Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "nodes/nodeFuncs.h"
#include "rewrite/rewriteManip.h"
#include "pg_ivm.h"
typedef struct inline_cte_walker_context
{
const char *ctename; /* name and relative level of target CTE */
int levelsup;
Query *ctequery; /* query to substitute */
} inline_cte_walker_context;
static bool inline_cte_walker(Node *node, inline_cte_walker_context *context);
/*
* inline_cte: convert RTE_CTE references to given CTE into RTE_SUBQUERYs
*/
void
inline_cte(PlannerInfo *root, CommonTableExpr *cte)
{
struct inline_cte_walker_context context;
context.ctename = cte->ctename;
/* Start at levelsup = -1 because we'll immediately increment it */
context.levelsup = -1;
context.ctequery = castNode(Query, cte->ctequery);
(void) inline_cte_walker((Node *) root->parse, &context);
}
static bool
inline_cte_walker(Node *node, inline_cte_walker_context *context)
{
if (node == NULL)
return false;
if (IsA(node, Query))
{
Query *query = (Query *) node;
context->levelsup++;
/*
* Visit the query's RTE nodes after their contents; otherwise
* query_tree_walker would descend into the newly inlined CTE query,
* which we don't want.
*/
(void) query_tree_walker(query, inline_cte_walker, context,
QTW_EXAMINE_RTES_AFTER);
context->levelsup--;
return false;
}
else if (IsA(node, RangeTblEntry))
{
RangeTblEntry *rte = (RangeTblEntry *) node;
if (rte->rtekind == RTE_CTE &&
strcmp(rte->ctename, context->ctename) == 0 &&
rte->ctelevelsup == context->levelsup)
{
/*
* Found a reference to replace. Generate a copy of the CTE query
* with appropriate level adjustment for outer references (e.g.,
* to other CTEs).
*/
Query *newquery = copyObject(context->ctequery);
if (context->levelsup > 0)
IncrementVarSublevelsUp((Node *) newquery, context->levelsup, 1);
/*
* Convert the RTE_CTE RTE into a RTE_SUBQUERY.
*
* Historically, a FOR UPDATE clause has been treated as extending
* into views and subqueries, but not into CTEs. We preserve this
* distinction by not trying to push rowmarks into the new
* subquery.
*/
rte->rtekind = RTE_SUBQUERY;
rte->subquery = newquery;
rte->security_barrier = false;
/* Zero out CTE-specific fields */
rte->ctename = NULL;
rte->ctelevelsup = 0;
rte->self_reference = false;
rte->coltypes = NIL;
rte->coltypmods = NIL;
rte->colcollations = NIL;
}
return false;
}
return expression_tree_walker(node, inline_cte_walker, context);
}
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