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postgresql/src/backend/optimizer/prep/preptlist.c

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/*-------------------------------------------------------------------------
*
* preptlist.c
* Routines to preprocess the parse tree target list
*
* For INSERT and UPDATE queries, the targetlist must contain an entry for
* each attribute of the target relation in the correct order. For UPDATE and
* DELETE queries, it must also contain junk tlist entries needed to allow the
* executor to identify the rows to be updated or deleted. For all query
* types, we may need to add junk tlist entries for Vars used in the RETURNING
* list and row ID information needed for SELECT FOR UPDATE locking and/or
* EvalPlanQual checking.
*
* The query rewrite phase also does preprocessing of the targetlist (see
* rewriteTargetListIU). The division of labor between here and there is
* partially historical, but it's not entirely arbitrary. In particular,
* consider an UPDATE across an inheritance tree. What rewriteTargetListIU
* does need be done only once (because it depends only on the properties of
* the parent relation). What's done here has to be done over again for each
* child relation, because it depends on the properties of the child, which
* might be of a different relation type, or have more columns and/or a
* different column order than the parent.
*
* The fact that rewriteTargetListIU sorts non-resjunk tlist entries by column
* position, which expand_targetlist depends on, violates the above comment
* because the sorting is only valid for the parent relation. In inherited
* UPDATE cases, adjust_inherited_tlist runs in between to take care of fixing
* the tlists for child tables to keep expand_targetlist happy. We do it like
* that because it's faster in typical non-inherited cases.
*
*
* Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* src/backend/optimizer/prep/preptlist.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/sysattr.h"
#include "access/table.h"
#include "catalog/pg_type.h"
#include "nodes/makefuncs.h"
#include "optimizer/optimizer.h"
#include "optimizer/prep.h"
#include "optimizer/tlist.h"
#include "parser/parse_coerce.h"
#include "parser/parsetree.h"
#include "rewrite/rewriteHandler.h"
#include "utils/rel.h"
static List *expand_targetlist(List *tlist, int command_type,
Index result_relation, Relation rel);
/*
* preprocess_targetlist
* Driver for preprocessing the parse tree targetlist.
*
* Returns the new targetlist.
*
* As a side effect, if there's an ON CONFLICT UPDATE clause, its targetlist
* is also preprocessed (and updated in-place).
*/
List *
preprocess_targetlist(PlannerInfo *root)
{
Query *parse = root->parse;
int result_relation = parse->resultRelation;
List *range_table = parse->rtable;
CmdType command_type = parse->commandType;
RangeTblEntry *target_rte = NULL;
Relation target_relation = NULL;
List *tlist;
ListCell *lc;
/*
* If there is a result relation, open it so we can look for missing
* columns and so on. We assume that previous code already acquired at
* least AccessShareLock on the relation, so we need no lock here.
*/
if (result_relation)
{
target_rte = rt_fetch(result_relation, range_table);
/*
* Sanity check: it'd better be a real relation not, say, a subquery.
* Else parser or rewriter messed up.
*/
if (target_rte->rtekind != RTE_RELATION)
elog(ERROR, "result relation must be a regular relation");
target_relation = table_open(target_rte->relid, NoLock);
}
else
Assert(command_type == CMD_SELECT);
/*
* For UPDATE/DELETE, add any junk column(s) needed to allow the executor
* to identify the rows to be updated or deleted. Note that this step
* scribbles on parse->targetList, which is not very desirable, but we
* keep it that way to avoid changing APIs used by FDWs.
*/
if (command_type == CMD_UPDATE || command_type == CMD_DELETE)
rewriteTargetListUD(parse, target_rte, target_relation);
/*
* for heap_form_tuple to work, the targetlist must match the exact order
* of the attributes. We also need to fill in any missing attributes. -ay
* 10/94
*/
tlist = parse->targetList;
if (command_type == CMD_INSERT || command_type == CMD_UPDATE)
tlist = expand_targetlist(tlist, command_type,
result_relation, target_relation);
/*
* Add necessary junk columns for rowmarked rels. These values are needed
* for locking of rels selected FOR UPDATE/SHARE, and to do EvalPlanQual
* rechecking. See comments for PlanRowMark in plannodes.h. If you
* change this stanza, see also expand_inherited_rtentry(), which has to
* be able to add on junk columns equivalent to these.
*/
foreach(lc, root->rowMarks)
{
PlanRowMark *rc = (PlanRowMark *) lfirst(lc);
Var *var;
char resname[32];
TargetEntry *tle;
/* child rels use the same junk attrs as their parents */
if (rc->rti != rc->prti)
continue;
if (rc->allMarkTypes & ~(1 << ROW_MARK_COPY))
{
/* Need to fetch TID */
var = makeVar(rc->rti,
SelfItemPointerAttributeNumber,
TIDOID,
-1,
InvalidOid,
0);
snprintf(resname, sizeof(resname), "ctid%u", rc->rowmarkId);
tle = makeTargetEntry((Expr *) var,
list_length(tlist) + 1,
pstrdup(resname),
true);
tlist = lappend(tlist, tle);
}
if (rc->allMarkTypes & (1 << ROW_MARK_COPY))
{
/* Need the whole row as a junk var */
var = makeWholeRowVar(rt_fetch(rc->rti, range_table),
rc->rti,
0,
false);
snprintf(resname, sizeof(resname), "wholerow%u", rc->rowmarkId);
tle = makeTargetEntry((Expr *) var,
list_length(tlist) + 1,
pstrdup(resname),
true);
tlist = lappend(tlist, tle);
}
/* If parent of inheritance tree, always fetch the tableoid too. */
if (rc->isParent)
{
var = makeVar(rc->rti,
TableOidAttributeNumber,
OIDOID,
-1,
InvalidOid,
0);
snprintf(resname, sizeof(resname), "tableoid%u", rc->rowmarkId);
tle = makeTargetEntry((Expr *) var,
list_length(tlist) + 1,
pstrdup(resname),
true);
tlist = lappend(tlist, tle);
}
}
/*
* If the query has a RETURNING list, add resjunk entries for any Vars
* used in RETURNING that belong to other relations. We need to do this
* to make these Vars available for the RETURNING calculation. Vars that
* belong to the result rel don't need to be added, because they will be
* made to refer to the actual heap tuple.
*/
if (parse->returningList && list_length(parse->rtable) > 1)
{
List *vars;
ListCell *l;
vars = pull_var_clause((Node *) parse->returningList,
PVC_RECURSE_AGGREGATES |
PVC_RECURSE_WINDOWFUNCS |
PVC_INCLUDE_PLACEHOLDERS);
foreach(l, vars)
{
Var *var = (Var *) lfirst(l);
TargetEntry *tle;
if (IsA(var, Var) &&
var->varno == result_relation)
continue; /* don't need it */
if (tlist_member((Expr *) var, tlist))
continue; /* already got it */
tle = makeTargetEntry((Expr *) var,
list_length(tlist) + 1,
NULL,
true);
tlist = lappend(tlist, tle);
}
list_free(vars);
}
/*
* If there's an ON CONFLICT UPDATE clause, preprocess its targetlist too
* while we have the relation open.
*/
if (parse->onConflict)
parse->onConflict->onConflictSet =
expand_targetlist(parse->onConflict->onConflictSet,
CMD_UPDATE,
result_relation,
target_relation);
if (target_relation)
table_close(target_relation, NoLock);
return tlist;
}
/*****************************************************************************
*
* TARGETLIST EXPANSION
*
*****************************************************************************/
/*
* expand_targetlist
* Given a target list as generated by the parser and a result relation,
* add targetlist entries for any missing attributes, and ensure the
* non-junk attributes appear in proper field order.
*/
static List *
expand_targetlist(List *tlist, int command_type,
Index result_relation, Relation rel)
{
List *new_tlist = NIL;
ListCell *tlist_item;
int attrno,
numattrs;
tlist_item = list_head(tlist);
/*
* The rewriter should have already ensured that the TLEs are in correct
* order; but we have to insert TLEs for any missing attributes.
*
* Scan the tuple description in the relation's relcache entry to make
* sure we have all the user attributes in the right order.
*/
numattrs = RelationGetNumberOfAttributes(rel);
for (attrno = 1; attrno <= numattrs; attrno++)
{
Form_pg_attribute att_tup = TupleDescAttr(rel->rd_att, attrno - 1);
TargetEntry *new_tle = NULL;
if (tlist_item != NULL)
{
TargetEntry *old_tle = (TargetEntry *) lfirst(tlist_item);
if (!old_tle->resjunk && old_tle->resno == attrno)
{
new_tle = old_tle;
tlist_item = lnext(tlist, tlist_item);
}
}
if (new_tle == NULL)
{
/*
* Didn't find a matching tlist entry, so make one.
*
* For INSERT, generate a NULL constant. (We assume the rewriter
* would have inserted any available default value.) Also, if the
* column isn't dropped, apply any domain constraints that might
* exist --- this is to catch domain NOT NULL.
*
* For UPDATE, generate a Var reference to the existing value of
* the attribute, so that it gets copied to the new tuple. But
* generate a NULL for dropped columns (we want to drop any old
* values).
*
* When generating a NULL constant for a dropped column, we label
* it INT4 (any other guaranteed-to-exist datatype would do as
* well). We can't label it with the dropped column's datatype
* since that might not exist anymore. It does not really matter
* what we claim the type is, since NULL is NULL --- its
* representation is datatype-independent. This could perhaps
* confuse code comparing the finished plan to the target
* relation, however.
*/
Oid atttype = att_tup->atttypid;
int32 atttypmod = att_tup->atttypmod;
Oid attcollation = att_tup->attcollation;
Node *new_expr;
switch (command_type)
{
case CMD_INSERT:
if (!att_tup->attisdropped)
{
new_expr = (Node *) makeConst(atttype,
-1,
attcollation,
att_tup->attlen,
(Datum) 0,
true, /* isnull */
att_tup->attbyval);
new_expr = coerce_to_domain(new_expr,
InvalidOid, -1,
atttype,
COERCION_IMPLICIT,
COERCE_IMPLICIT_CAST,
-1,
false);
}
else
{
/* Insert NULL for dropped column */
new_expr = (Node *) makeConst(INT4OID,
-1,
InvalidOid,
sizeof(int32),
(Datum) 0,
true, /* isnull */
true /* byval */ );
}
break;
case CMD_UPDATE:
if (!att_tup->attisdropped)
{
new_expr = (Node *) makeVar(result_relation,
attrno,
atttype,
atttypmod,
attcollation,
0);
}
else
{
/* Insert NULL for dropped column */
new_expr = (Node *) makeConst(INT4OID,
-1,
InvalidOid,
sizeof(int32),
(Datum) 0,
true, /* isnull */
true /* byval */ );
}
break;
default:
elog(ERROR, "unrecognized command_type: %d",
(int) command_type);
new_expr = NULL; /* keep compiler quiet */
break;
}
new_tle = makeTargetEntry((Expr *) new_expr,
attrno,
pstrdup(NameStr(att_tup->attname)),
false);
}
new_tlist = lappend(new_tlist, new_tle);
}
/*
* The remaining tlist entries should be resjunk; append them all to the
* end of the new tlist, making sure they have resnos higher than the last
* real attribute. (Note: although the rewriter already did such
* renumbering, we have to do it again here in case we are doing an UPDATE
* in a table with dropped columns, or an inheritance child table with
* extra columns.)
*/
while (tlist_item)
{
TargetEntry *old_tle = (TargetEntry *) lfirst(tlist_item);
if (!old_tle->resjunk)
elog(ERROR, "targetlist is not sorted correctly");
/* Get the resno right, but don't copy unnecessarily */
if (old_tle->resno != attrno)
{
old_tle = flatCopyTargetEntry(old_tle);
old_tle->resno = attrno;
}
new_tlist = lappend(new_tlist, old_tle);
attrno++;
tlist_item = lnext(tlist, tlist_item);
}
return new_tlist;
}
/*
* Locate PlanRowMark for given RT index, or return NULL if none
*
* This probably ought to be elsewhere, but there's no very good place
*/
PlanRowMark *
get_plan_rowmark(List *rowmarks, Index rtindex)
{
ListCell *l;
foreach(l, rowmarks)
{
PlanRowMark *rc = (PlanRowMark *) lfirst(l);
if (rc->rti == rtindex)
return rc;
}
return NULL;
}
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