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Eliminate code duplication in replace_rte_variables callbacks

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The callback functions ReplaceVarsFromTargetList_callback and
pullup_replace_vars_callback are both used to replace Vars in an
expression tree that reference a particular RTE with items from a
targetlist, and they both need to expand whole-tuple references and
deal with OLD/NEW RETURNING list Vars.  As a result, currently there
is significant code duplication between these two functions.

This patch introduces a new function, ReplaceVarFromTargetList, to
perform the replacement and calls it from both callback functions,
thereby eliminating code duplication.

Author: Dean Rasheed <dean.a.rasheed@gmail.com>
Author: Richard Guo <guofenglinux@gmail.com>
Reviewed-by: Jian He <jian.universality@gmail.com>
Discussion: https://postgr.es/m/CAEZATCWhr=FM4X5kCPvVs-g2XEk+ceLsNtBK_zZMkqFn9vUjsw@mail.gmail.com
This commit is contained in:
Richard Guo
2025-02-25 16:11:34 +09:00
parent 1e4351af32
commit 363a6e8c6f
3 changed files with 97 additions and 143 deletions
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88
src/backend/rewrite/rewriteManip.c
View File

@@ -1010,7 +1010,7 @@ SetVarReturningType_walker(Node *node, SetVarReturningType_context *context)
return expression_tree_walker(node, SetVarReturningType_walker, context);
}
void
static void
SetVarReturningType(Node *node, int result_relation, int sublevels_up,
VarReturningType returning_type)
{
@@ -1797,6 +1797,11 @@ map_variable_attnos(Node *node,
* referencing result_relation, it is wrapped in a ReturningExpr node (causing
* the executor to return NULL if the OLD/NEW row doesn't exist).
*
* Note that ReplaceVarFromTargetList always generates the replacement
* expression with varlevelsup = 0. The caller is responsible for adjusting
* the varlevelsup if needed. This simplifies the caller's life if it wants to
* cache the replacement expressions.
*
* outer_hasSubLinks works the same as for replace_rte_variables().
*/
@@ -1814,6 +1819,30 @@ ReplaceVarsFromTargetList_callback(Var *var,
replace_rte_variables_context *context)
{
ReplaceVarsFromTargetList_context *rcon = (ReplaceVarsFromTargetList_context *) context->callback_arg;
Node *newnode;
newnode = ReplaceVarFromTargetList(var,
rcon->target_rte,
rcon->targetlist,
rcon->result_relation,
rcon->nomatch_option,
rcon->nomatch_varno);
/* Must adjust varlevelsup if replaced Var is within a subquery */
if (var->varlevelsup > 0)
IncrementVarSublevelsUp(newnode, var->varlevelsup, 0);
return newnode;
}
Node *
ReplaceVarFromTargetList(Var *var,
RangeTblEntry *target_rte,
List *targetlist,
int result_relation,
ReplaceVarsNoMatchOption nomatch_option,
int nomatch_varno)
{
TargetEntry *tle;
if (var->varattno == InvalidAttrNumber)
@@ -1822,6 +1851,7 @@ ReplaceVarsFromTargetList_callback(Var *var,
RowExpr *rowexpr;
List *colnames;
List *fields;
ListCell *lc;
/*
* If generating an expansion for a var of a named rowtype (ie, this
@@ -1830,29 +1860,46 @@ ReplaceVarsFromTargetList_callback(Var *var,
* omit dropped columns. In the latter case, attach column names to
* the RowExpr for use of the executor and ruleutils.c.
*
* In order to be able to cache the results, we always generate the
* expansion with varlevelsup = 0. The caller is responsible for
* adjusting it if needed.
*
* The varreturningtype is copied onto each individual field Var, so
* that it is handled correctly when we recurse.
*/
expandRTE(rcon->target_rte,
var->varno, var->varlevelsup, var->varreturningtype,
var->location, (var->vartype != RECORDOID),
expandRTE(target_rte,
var->varno, 0 /* not varlevelsup */ ,
var->varreturningtype, var->location,
(var->vartype != RECORDOID),
&colnames, &fields);
/* Adjust the generated per-field Vars... */
fields = (List *) replace_rte_variables_mutator((Node *) fields,
context);
rowexpr = makeNode(RowExpr);
rowexpr->args = fields;
/* the fields will be set below */
rowexpr->args = NIL;
rowexpr->row_typeid = var->vartype;
rowexpr->row_format = COERCE_IMPLICIT_CAST;
rowexpr->colnames = (var->vartype == RECORDOID) ? colnames : NIL;
rowexpr->location = var->location;
/* Adjust the generated per-field Vars... */
foreach(lc, fields)
{
Node *field = lfirst(lc);
if (field && IsA(field, Var))
field = ReplaceVarFromTargetList((Var *) field,
target_rte,
targetlist,
result_relation,
nomatch_option,
nomatch_varno);
rowexpr->args = lappend(rowexpr->args, field);
}
/* Wrap it in a ReturningExpr, if needed, per comments above */
if (var->varreturningtype != VAR_RETURNING_DEFAULT)
{
ReturningExpr *rexpr = makeNode(ReturningExpr);
rexpr->retlevelsup = var->varlevelsup;
rexpr->retlevelsup = 0;
rexpr->retold = (var->varreturningtype == VAR_RETURNING_OLD);
rexpr->retexpr = (Expr *) rowexpr;
@@ -1863,12 +1910,12 @@ ReplaceVarsFromTargetList_callback(Var *var,
}
/* Normal case referencing one targetlist element */
tle = get_tle_by_resno(rcon->targetlist, var->varattno);
tle = get_tle_by_resno(targetlist, var->varattno);
if (tle == NULL || tle->resjunk)
{
/* Failed to find column in targetlist */
switch (rcon->nomatch_option)
switch (nomatch_option)
{
case REPLACEVARS_REPORT_ERROR:
/* fall through, throw error below */
@@ -1876,7 +1923,8 @@ ReplaceVarsFromTargetList_callback(Var *var,
case REPLACEVARS_CHANGE_VARNO:
var = copyObject(var);
var->varno = rcon->nomatch_varno;
var->varno = nomatch_varno;
var->varlevelsup = 0;
/* we leave the syntactic referent alone */
return (Node *) var;
@@ -1906,10 +1954,6 @@ ReplaceVarsFromTargetList_callback(Var *var,
/* Make a copy of the tlist item to return */
Expr *newnode = copyObject(tle->expr);
/* Must adjust varlevelsup if tlist item is from higher query */
if (var->varlevelsup > 0)
IncrementVarSublevelsUp((Node *) newnode, var->varlevelsup, 0);
/*
* Check to see if the tlist item contains a PARAM_MULTIEXPR Param,
* and throw error if so. This case could only happen when expanding
@@ -1932,20 +1976,20 @@ ReplaceVarsFromTargetList_callback(Var *var,
* Copy varreturningtype onto any Vars in the tlist item that
* refer to result_relation (which had better be non-zero).
*/
if (rcon->result_relation == 0)
if (result_relation == 0)
elog(ERROR, "variable returning old/new found outside RETURNING list");
SetVarReturningType((Node *) newnode, rcon->result_relation,
var->varlevelsup, var->varreturningtype);
SetVarReturningType((Node *) newnode, result_relation,
0, var->varreturningtype);
/* Wrap it in a ReturningExpr, if needed, per comments above */
if (!IsA(newnode, Var) ||
((Var *) newnode)->varno != rcon->result_relation ||
((Var *) newnode)->varlevelsup != var->varlevelsup)
((Var *) newnode)->varno != result_relation ||
((Var *) newnode)->varlevelsup != 0)
{
ReturningExpr *rexpr = makeNode(ReturningExpr);
rexpr->retlevelsup = var->varlevelsup;
rexpr->retlevelsup = 0;
rexpr->retold = (var->varreturningtype == VAR_RETURNING_OLD);
rexpr->retexpr = newnode;