Re: Allow an alias to be attached directly to a JOIN ... USING - Mailing list pgsql-hackers
| From | Tom Lane |
|---|---|
| Subject | Re: Allow an alias to be attached directly to a JOIN ... USING |
| Date | |
| Msg-id | 785329.1616455091@sss.pgh.pa.us Whole thread Raw |
| In response to | Re: Allow an alias to be attached directly to a JOIN ... USING (Peter Eisentraut <peter.eisentraut@2ndquadrant.com>) |
| Responses |
Re: Allow an alias to be attached directly to a JOIN ... USING
(Peter Eisentraut <peter.eisentraut@2ndquadrant.com>)
|
| List | pgsql-hackers |
Peter Eisentraut <peter.eisentraut@2ndquadrant.com> writes:
> I think Tom's input on the guts of this patch would be most valuable,
> since it intersects a lot with the parse namespace refactoring he did.
I really didn't like the way you'd done that :-(. My primary complaint
is that any one ParseNamespaceItem can describe only one table alias,
but here we have the potential for two aliases associated with the same
join:
select * from (t1 join t2 using(a) as tu) tx;
Admittedly that's not hugely useful since tx hides the tu alias, but
it should behave in a sane fashion. (BTW, after reading the SQL spec
again along the way to reviewing this, I am wondering if hiding the
lower aliases is really what we want; though it may be decades too late
to change that.)
However, ParseNamespaceItem as it stands needs some help for this.
It has a wired-in assumption that p_rte->eref describes the table
and column aliases exposed by the nsitem. 0001 below fixes this by
creating a separate p_names field in an nsitem. (There are some
comments in 0001 referencing JOIN USING aliases, but no actual code
for the feature.) That saves one indirection in common code paths,
so it's possibly a win on its own. Then 0002 is your patch rebased
onto that infrastructure, and with some cleanup of my own.
One thing I ran into is that a whole-row Var for the JOIN USING
alias did the wrong thing. It should have only the common columns,
but we were getting all the join columns in examples such as the
row_to_json() test case I added. This is difficult to fix given
the existing whole-row Var infrastructure, unless we want to make a
separate RTE for the JOIN USING alias, which I think is overkill.
What I did about this was to make transformWholeRowRef produce a
ROW() construct --- which is something that a whole-row Var for a
join would be turned into by the planner anyway. I think this is
semantically OK since the USING construct has already nailed down
the number and types of the join's common columns; there's no
prospect of those changing underneath a stored view query. It's
slightly ugly because the ROW() construct will be visible in a
decompiled view instead of "tu.*" like you wrote originally,
but I'm willing to live with that.
Speaking of decompiled views, I feel like ruleutils.c could do with
a little more work to teach it that these aliases are available.
Right now, it resorts to ugly workarounds:
regression=# create table t1 (a int, b int, c int);
CREATE TABLE
regression=# create table t2 (a int, x int, y int);
CREATE TABLE
regression=# create view vvv as select tj.a, t1.b from t1 full join t2 using(a) as tj, t1 as tx;
CREATE VIEW
regression=# \d+ vvv
View "public.vvv"
Column | Type | Collation | Nullable | Default | Storage | Description
--------+---------+-----------+----------+---------+---------+-------------
a | integer | | | | plain |
b | integer | | | | plain |
View definition:
SELECT a,
t1.b
FROM t1
FULL JOIN t2 USING (a) AS tj,
t1 tx(a_1, b, c);
That's not wrong, but it could likely be done better if ruleutils
realized it could use the tj alias to reference the column, instead
of having to force unqualified "a" to be a globally unique name.
I ran out of steam to look into that, though, and it's probably
something that could be improved later.
One other cosmetic thing is that this:
regression=# select tu.* from (t1 join t2 using(a) as tu) tx;
ERROR: missing FROM-clause entry for table "tu"
LINE 1: select tu.* from (t1 join t2 using(a) as tu) tx;
^
is a relatively dumb error message, compared to
regression=# select t1.* from (t1 join t2 using(a) as tu) tx;
ERROR: invalid reference to FROM-clause entry for table "t1"
LINE 1: select t1.* from (t1 join t2 using(a) as tu) tx;
^
HINT: There is an entry for table "t1", but it cannot be referenced from this part of the query.
I didn't look into why that isn't working, but maybe errorMissingRTE
needs to trawl all of the ParseNamespaceItems not just the RTEs.
Anyway, since these remaining gripes are cosmetic, I'll mark this RFC.
regards, tom lane
diff --git a/src/backend/parser/parse_clause.c b/src/backend/parser/parse_clause.c
index bdf8ec46e2..5dfea46021 100644
--- a/src/backend/parser/parse_clause.c
+++ b/src/backend/parser/parse_clause.c
@@ -1217,9 +1217,9 @@ transformFromClauseItem(ParseState *pstate, Node *n,
* input column numbers more easily.
*/
l_nscolumns = l_nsitem->p_nscolumns;
- l_colnames = l_nsitem->p_rte->eref->colnames;
+ l_colnames = l_nsitem->p_names->colnames;
r_nscolumns = r_nsitem->p_nscolumns;
- r_colnames = r_nsitem->p_rte->eref->colnames;
+ r_colnames = r_nsitem->p_names->colnames;
/*
* Natural join does not explicitly specify columns; must generate
@@ -1469,7 +1469,7 @@ transformFromClauseItem(ParseState *pstate, Node *n,
* Now that we know the join RTE's rangetable index, we can fix up the
* res_nscolumns data in places where it should contain that.
*/
- Assert(res_colindex == list_length(nsitem->p_rte->eref->colnames));
+ Assert(res_colindex == list_length(nsitem->p_names->colnames));
for (k = 0; k < res_colindex; k++)
{
ParseNamespaceColumn *nscol = res_nscolumns + k;
diff --git a/src/backend/parser/parse_expr.c b/src/backend/parser/parse_expr.c
index f869e159d6..b38d919621 100644
--- a/src/backend/parser/parse_expr.c
+++ b/src/backend/parser/parse_expr.c
@@ -2518,6 +2518,7 @@ transformWholeRowRef(ParseState *pstate, ParseNamespaceItem *nsitem,
* historically. One argument for it is that "rel" and "rel.*" mean the
* same thing for composite relations, so why not for scalar functions...
*/
+ /* XXX wrong for join alias case! */
result = makeWholeRowVar(nsitem->p_rte, nsitem->p_rtindex,
sublevels_up, true);
diff --git a/src/backend/parser/parse_relation.c b/src/backend/parser/parse_relation.c
index ca02982e0b..17232f027e 100644
--- a/src/backend/parser/parse_relation.c
+++ b/src/backend/parser/parse_relation.c
@@ -65,6 +65,7 @@ static ParseNamespaceItem *scanNameSpaceForRelid(ParseState *pstate, Oid relid,
static void check_lateral_ref_ok(ParseState *pstate, ParseNamespaceItem *nsitem,
int location);
static int scanRTEForColumn(ParseState *pstate, RangeTblEntry *rte,
+ Alias *eref,
const char *colname, int location,
int fuzzy_rte_penalty,
FuzzyAttrMatchState *fuzzystate);
@@ -184,7 +185,6 @@ scanNameSpaceForRefname(ParseState *pstate, const char *refname, int location)
foreach(l, pstate->p_namespace)
{
ParseNamespaceItem *nsitem = (ParseNamespaceItem *) lfirst(l);
- RangeTblEntry *rte = nsitem->p_rte;
/* Ignore columns-only items */
if (!nsitem->p_rel_visible)
@@ -193,7 +193,7 @@ scanNameSpaceForRefname(ParseState *pstate, const char *refname, int location)
if (nsitem->p_lateral_only && !pstate->p_lateral_active)
continue;
- if (strcmp(rte->eref->aliasname, refname) == 0)
+ if (strcmp(nsitem->p_names->aliasname, refname) == 0)
{
if (result)
ereport(ERROR,
@@ -420,7 +420,7 @@ checkNameSpaceConflicts(ParseState *pstate, List *namespace1,
{
ParseNamespaceItem *nsitem1 = (ParseNamespaceItem *) lfirst(l1);
RangeTblEntry *rte1 = nsitem1->p_rte;
- const char *aliasname1 = rte1->eref->aliasname;
+ const char *aliasname1 = nsitem1->p_names->aliasname;
ListCell *l2;
if (!nsitem1->p_rel_visible)
@@ -430,10 +430,11 @@ checkNameSpaceConflicts(ParseState *pstate, List *namespace1,
{
ParseNamespaceItem *nsitem2 = (ParseNamespaceItem *) lfirst(l2);
RangeTblEntry *rte2 = nsitem2->p_rte;
+ const char *aliasname2 = nsitem2->p_names->aliasname;
if (!nsitem2->p_rel_visible)
continue;
- if (strcmp(rte2->eref->aliasname, aliasname1) != 0)
+ if (strcmp(aliasname2, aliasname1) != 0)
continue; /* definitely no conflict */
if (rte1->rtekind == RTE_RELATION && rte1->alias == NULL &&
rte2->rtekind == RTE_RELATION && rte2->alias == NULL &&
@@ -466,7 +467,7 @@ check_lateral_ref_ok(ParseState *pstate, ParseNamespaceItem *nsitem,
{
/* SQL:2008 demands this be an error, not an invisible item */
RangeTblEntry *rte = nsitem->p_rte;
- char *refname = rte->eref->aliasname;
+ char *refname = nsitem->p_names->aliasname;
ereport(ERROR,
(errcode(ERRCODE_INVALID_COLUMN_REFERENCE),
@@ -672,10 +673,10 @@ scanNSItemForColumn(ParseState *pstate, ParseNamespaceItem *nsitem,
Var *var;
/*
- * Scan the RTE's column names (or aliases) for a match. Complain if
+ * Scan the nsitem's column names (or aliases) for a match. Complain if
* multiple matches.
*/
- attnum = scanRTEForColumn(pstate, rte,
+ attnum = scanRTEForColumn(pstate, rte, nsitem->p_names,
colname, location,
0, NULL);
@@ -712,7 +713,7 @@ scanNSItemForColumn(ParseState *pstate, ParseNamespaceItem *nsitem,
(errcode(ERRCODE_UNDEFINED_COLUMN),
errmsg("column \"%s\" of relation \"%s\" does not exist",
colname,
- rte->eref->aliasname)));
+ nsitem->p_names->aliasname)));
var = makeVar(nscol->p_varno,
nscol->p_varattno,
@@ -752,6 +753,12 @@ scanNSItemForColumn(ParseState *pstate, ParseNamespaceItem *nsitem,
* else return InvalidAttrNumber.
* If the name proves ambiguous within this RTE, raise error.
*
+ * Actually, we only search the names listed in "eref". This can be either
+ * rte->eref, in which case we are indeed searching all the column names,
+ * or for a join it can be rte->join_using_alias, in which case we are only
+ * considering the common column names (which are the first N columns of the
+ * join, so everything works).
+ *
* pstate and location are passed only for error-reporting purposes.
*
* Side effect: if fuzzystate is non-NULL, check non-system columns
@@ -765,6 +772,7 @@ scanNSItemForColumn(ParseState *pstate, ParseNamespaceItem *nsitem,
*/
static int
scanRTEForColumn(ParseState *pstate, RangeTblEntry *rte,
+ Alias *eref,
const char *colname, int location,
int fuzzy_rte_penalty,
FuzzyAttrMatchState *fuzzystate)
@@ -786,7 +794,7 @@ scanRTEForColumn(ParseState *pstate, RangeTblEntry *rte,
* Callers interested in finding match with shortest distance need to
* defend against this directly, though.
*/
- foreach(c, rte->eref->colnames)
+ foreach(c, eref->colnames)
{
const char *attcolname = strVal(lfirst(c));
@@ -970,7 +978,7 @@ searchRangeTableForCol(ParseState *pstate, const char *alias, const char *colnam
* Scan for a matching column; if we find an exact match, we're
* done. Otherwise, update fuzzystate.
*/
- if (scanRTEForColumn(orig_pstate, rte, colname, location,
+ if (scanRTEForColumn(orig_pstate, rte, rte->eref, colname, location,
fuzzy_rte_penalty, fuzzystate)
&& fuzzy_rte_penalty == 0)
{
@@ -1252,6 +1260,7 @@ buildNSItemFromTupleDesc(RangeTblEntry *rte, Index rtindex, TupleDesc tupdesc)
/* ... and build the nsitem */
nsitem = (ParseNamespaceItem *) palloc(sizeof(ParseNamespaceItem));
+ nsitem->p_names = rte->eref;
nsitem->p_rte = rte;
nsitem->p_rtindex = rtindex;
nsitem->p_nscolumns = nscolumns;
@@ -1313,6 +1322,7 @@ buildNSItemFromLists(RangeTblEntry *rte, Index rtindex,
/* ... and build the nsitem */
nsitem = (ParseNamespaceItem *) palloc(sizeof(ParseNamespaceItem));
+ nsitem->p_names = rte->eref;
nsitem->p_rte = rte;
nsitem->p_rtindex = rtindex;
nsitem->p_nscolumns = nscolumns;
@@ -2198,6 +2208,7 @@ addRangeTableEntryForJoin(ParseState *pstate,
* list --- caller must do that if appropriate.
*/
nsitem = (ParseNamespaceItem *) palloc(sizeof(ParseNamespaceItem));
+ nsitem->p_names = rte->eref;
nsitem->p_rte = rte;
nsitem->p_rtindex = list_length(pstate->p_rtable);
nsitem->p_nscolumns = nscolumns;
@@ -2356,7 +2367,7 @@ addRangeTableEntryForCTE(ParseState *pstate,
*/
if (rte->ctelevelsup > 0)
for (int i = 0; i < n_dontexpand_columns; i++)
- psi->p_nscolumns[list_length(psi->p_rte->eref->colnames) - 1 - i].p_dontexpand = true;
+ psi->p_nscolumns[list_length(psi->p_names->colnames) - 1 - i].p_dontexpand = true;
return psi;
}
@@ -3037,7 +3048,7 @@ expandNSItemVars(ParseNamespaceItem *nsitem,
if (colnames)
*colnames = NIL;
colindex = 0;
- foreach(lc, nsitem->p_rte->eref->colnames)
+ foreach(lc, nsitem->p_names->colnames)
{
Value *colnameval = (Value *) lfirst(lc);
const char *colname = strVal(colnameval);
diff --git a/src/include/parser/parse_node.h b/src/include/parser/parse_node.h
index 176b9f37c1..03a7f5bb1a 100644
--- a/src/include/parser/parse_node.h
+++ b/src/include/parser/parse_node.h
@@ -226,8 +226,16 @@ struct ParseState
/*
* An element of a namespace list.
*
+ * p_names contains the table name and column names exposed by this nsitem.
+ * (Typically it's equal to p_rte->eref, but for a JOIN USING alias it's
+ * equal to p_rte->join_using_alias. Since the USING columns will be the
+ * join's first N columns, the net effect is just that we expose only those
+ * join columns via this nsitem.)
+ *
+ * p_rte and p_rtindex link to the underlying rangetable entry.
+ *
* The p_nscolumns array contains info showing how to construct Vars
- * referencing corresponding elements of the RTE's colnames list.
+ * referencing the names appearing in the p_names->colnames list.
*
* Namespace items with p_rel_visible set define which RTEs are accessible by
* qualified names, while those with p_cols_visible set define which RTEs are
@@ -255,9 +263,10 @@ struct ParseState
*/
struct ParseNamespaceItem
{
+ Alias *p_names; /* Table and column names */
RangeTblEntry *p_rte; /* The relation's rangetable entry */
int p_rtindex; /* The relation's index in the rangetable */
- /* array of same length as p_rte->eref->colnames: */
+ /* array of same length as p_names->colnames: */
ParseNamespaceColumn *p_nscolumns; /* per-column data */
bool p_rel_visible; /* Relation name is visible? */
bool p_cols_visible; /* Column names visible as unqualified refs? */
diff --git a/doc/src/sgml/ref/select.sgml b/doc/src/sgml/ref/select.sgml
index 9c5cf50ef0..869941bc22 100644
--- a/doc/src/sgml/ref/select.sgml
+++ b/doc/src/sgml/ref/select.sgml
@@ -59,7 +59,7 @@ SELECT [ ALL | DISTINCT [ ON ( <replaceable class="parameter">expression</replac
[ LATERAL ] <replaceable class="parameter">function_name</replaceable> ( [ <replaceable
class="parameter">argument</replaceable>[, ...] ] ) AS ( <replaceable class="parameter">column_definition</replaceable>
[,...] )
[ LATERAL ] ROWS FROM( <replaceable class="parameter">function_name</replaceable> ( [ <replaceable
class="parameter">argument</replaceable>[, ...] ] ) [ AS ( <replaceable
class="parameter">column_definition</replaceable>[, ...] ) ] [, ...] )
[ WITH ORDINALITY ] [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable
class="parameter">column_alias</replaceable>[, ...] ) ] ]
- <replaceable class="parameter">from_item</replaceable> [ NATURAL ] <replaceable
class="parameter">join_type</replaceable><replaceable class="parameter">from_item</replaceable> [ ON <replaceable
class="parameter">join_condition</replaceable>| USING ( <replaceable class="parameter">join_column</replaceable> [,
...]) ]
+ <replaceable class="parameter">from_item</replaceable> [ NATURAL ] <replaceable
class="parameter">join_type</replaceable><replaceable class="parameter">from_item</replaceable> [ ON <replaceable
class="parameter">join_condition</replaceable>| USING ( <replaceable class="parameter">join_column</replaceable> [,
...]) [ AS <replaceable class="parameter">join_using_alias</replaceable> ] ]
<phrase>and <replaceable class="parameter">grouping_element</replaceable> can be one of:</phrase>
@@ -676,7 +676,7 @@ TABLE [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ]
</varlistentry>
<varlistentry>
- <term><literal>USING ( <replaceable class="parameter">join_column</replaceable> [, ...] )</literal></term>
+ <term><literal>USING ( <replaceable class="parameter">join_column</replaceable> [, ...] ) [ AS <replaceable
class="parameter">join_using_alias</replaceable>]</literal></term>
<listitem>
<para>
A clause of the form <literal>USING ( a, b, ... )</literal> is
@@ -686,6 +686,20 @@ TABLE [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ]
equivalent columns will be included in the join output, not
both.
</para>
+
+ <para>
+ If a <replaceable class="parameter">join_using_alias</replaceable>
+ name is specified, it provides a table alias for the join columns.
+ Only the join columns listed in the <literal>USING</literal> clause
+ are addressable by this name. Unlike a
+ regular <replaceable class="parameter">alias</replaceable>, this does
+ not hide the names of the joined tables from the rest of the query.
+ Also unlike a
+ regular <replaceable class="parameter">alias</replaceable>, you
+ cannot write a column alias list — the output names of the join
+ columns are the same as they appear in the <literal>USING</literal>
+ list.
+ </para>
</listitem>
</varlistentry>
diff --git a/src/backend/catalog/sql_features.txt b/src/backend/catalog/sql_features.txt
index b7165404cd..657e6c734b 100644
--- a/src/backend/catalog/sql_features.txt
+++ b/src/backend/catalog/sql_features.txt
@@ -264,7 +264,7 @@ F401 Extended joined table 02 FULL OUTER JOIN YES
F401 Extended joined table 04 CROSS JOIN YES
F402 Named column joins for LOBs, arrays, and multisets YES
F403 Partitioned joined tables NO
-F404 Range variable for common column names NO
+F404 Range variable for common column names YES
F411 Time zone specification YES differences regarding literal interpretation
F421 National character YES
F431 Read-only scrollable cursors YES
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 2c20541e92..732c262265 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -2230,6 +2230,7 @@ _copyJoinExpr(const JoinExpr *from)
COPY_NODE_FIELD(larg);
COPY_NODE_FIELD(rarg);
COPY_NODE_FIELD(usingClause);
+ COPY_NODE_FIELD(join_using_alias);
COPY_NODE_FIELD(quals);
COPY_NODE_FIELD(alias);
COPY_SCALAR_FIELD(rtindex);
@@ -2440,6 +2441,7 @@ _copyRangeTblEntry(const RangeTblEntry *from)
COPY_NODE_FIELD(joinaliasvars);
COPY_NODE_FIELD(joinleftcols);
COPY_NODE_FIELD(joinrightcols);
+ COPY_NODE_FIELD(join_using_alias);
COPY_NODE_FIELD(functions);
COPY_SCALAR_FIELD(funcordinality);
COPY_NODE_FIELD(tablefunc);
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index 3e980c457c..75b7592cb4 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -790,6 +790,7 @@ _equalJoinExpr(const JoinExpr *a, const JoinExpr *b)
COMPARE_NODE_FIELD(larg);
COMPARE_NODE_FIELD(rarg);
COMPARE_NODE_FIELD(usingClause);
+ COMPARE_NODE_FIELD(join_using_alias);
COMPARE_NODE_FIELD(quals);
COMPARE_NODE_FIELD(alias);
COMPARE_SCALAR_FIELD(rtindex);
@@ -2693,6 +2694,7 @@ _equalRangeTblEntry(const RangeTblEntry *a, const RangeTblEntry *b)
COMPARE_NODE_FIELD(joinaliasvars);
COMPARE_NODE_FIELD(joinleftcols);
COMPARE_NODE_FIELD(joinrightcols);
+ COMPARE_NODE_FIELD(join_using_alias);
COMPARE_NODE_FIELD(functions);
COMPARE_SCALAR_FIELD(funcordinality);
COMPARE_NODE_FIELD(tablefunc);
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index 305311d4a7..edc569297f 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -1692,6 +1692,7 @@ _outJoinExpr(StringInfo str, const JoinExpr *node)
WRITE_NODE_FIELD(larg);
WRITE_NODE_FIELD(rarg);
WRITE_NODE_FIELD(usingClause);
+ WRITE_NODE_FIELD(join_using_alias);
WRITE_NODE_FIELD(quals);
WRITE_NODE_FIELD(alias);
WRITE_INT_FIELD(rtindex);
@@ -3182,6 +3183,7 @@ _outRangeTblEntry(StringInfo str, const RangeTblEntry *node)
WRITE_NODE_FIELD(joinaliasvars);
WRITE_NODE_FIELD(joinleftcols);
WRITE_NODE_FIELD(joinrightcols);
+ WRITE_NODE_FIELD(join_using_alias);
break;
case RTE_FUNCTION:
WRITE_NODE_FIELD(functions);
diff --git a/src/backend/nodes/readfuncs.c b/src/backend/nodes/readfuncs.c
index 9b8f81c523..5e1274b872 100644
--- a/src/backend/nodes/readfuncs.c
+++ b/src/backend/nodes/readfuncs.c
@@ -1346,6 +1346,7 @@ _readJoinExpr(void)
READ_NODE_FIELD(larg);
READ_NODE_FIELD(rarg);
READ_NODE_FIELD(usingClause);
+ READ_NODE_FIELD(join_using_alias);
READ_NODE_FIELD(quals);
READ_NODE_FIELD(alias);
READ_INT_FIELD(rtindex);
@@ -1449,6 +1450,7 @@ _readRangeTblEntry(void)
READ_NODE_FIELD(joinaliasvars);
READ_NODE_FIELD(joinleftcols);
READ_NODE_FIELD(joinrightcols);
+ READ_NODE_FIELD(join_using_alias);
break;
case RTE_FUNCTION:
READ_NODE_FIELD(functions);
diff --git a/src/backend/optimizer/plan/setrefs.c b/src/backend/optimizer/plan/setrefs.c
index 42f088ad71..018af8f1eb 100644
--- a/src/backend/optimizer/plan/setrefs.c
+++ b/src/backend/optimizer/plan/setrefs.c
@@ -457,6 +457,7 @@ add_rte_to_flat_rtable(PlannerGlobal *glob, RangeTblEntry *rte)
newrte->joinaliasvars = NIL;
newrte->joinleftcols = NIL;
newrte->joinrightcols = NIL;
+ newrte->join_using_alias = NULL;
newrte->functions = NIL;
newrte->tablefunc = NULL;
newrte->values_lists = NIL;
diff --git a/src/backend/optimizer/plan/subselect.c b/src/backend/optimizer/plan/subselect.c
index f3e46e0959..9bb84c4c30 100644
--- a/src/backend/optimizer/plan/subselect.c
+++ b/src/backend/optimizer/plan/subselect.c
@@ -1365,6 +1365,7 @@ convert_ANY_sublink_to_join(PlannerInfo *root, SubLink *sublink,
result->larg = NULL; /* caller must fill this in */
result->rarg = (Node *) rtr;
result->usingClause = NIL;
+ result->join_using_alias = NULL;
result->quals = quals;
result->alias = NULL;
result->rtindex = 0; /* we don't need an RTE for it */
@@ -1519,6 +1520,7 @@ convert_EXISTS_sublink_to_join(PlannerInfo *root, SubLink *sublink,
else
result->rarg = (Node *) subselect->jointree;
result->usingClause = NIL;
+ result->join_using_alias = NULL;
result->quals = whereClause;
result->alias = NULL;
result->rtindex = 0; /* we don't need an RTE for it */
diff --git a/src/backend/parser/analyze.c b/src/backend/parser/analyze.c
index 7149724953..5de1307570 100644
--- a/src/backend/parser/analyze.c
+++ b/src/backend/parser/analyze.c
@@ -1744,6 +1744,7 @@ transformSetOperationStmt(ParseState *pstate, SelectStmt *stmt)
NIL,
NIL,
NULL,
+ NULL,
false);
sv_namespace = pstate->p_namespace;
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index bc43641ffe..815ba470e4 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -508,7 +508,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
%type <ival> sub_type opt_materialized
%type <value> NumericOnly
%type <list> NumericOnly_list
-%type <alias> alias_clause opt_alias_clause
+%type <alias> alias_clause opt_alias_clause opt_alias_clause_for_join_using
%type <list> func_alias_clause
%type <sortby> sortby
%type <ielem> index_elem index_elem_options
@@ -12097,6 +12097,7 @@ joined_table:
n->larg = $1;
n->rarg = $4;
n->usingClause = NIL;
+ n->join_using_alias = NULL;
n->quals = NULL;
$$ = n;
}
@@ -12108,9 +12109,16 @@ joined_table:
n->larg = $1;
n->rarg = $4;
if ($5 != NULL && IsA($5, List))
- n->usingClause = (List *) $5; /* USING clause */
+ {
+ /* USING clause */
+ n->usingClause = linitial_node(List, castNode(List, $5));
+ n->join_using_alias = lsecond_node(Alias, castNode(List, $5));
+ }
else
- n->quals = $5; /* ON clause */
+ {
+ /* ON clause */
+ n->quals = $5;
+ }
$$ = n;
}
| table_ref JOIN table_ref join_qual
@@ -12122,9 +12130,16 @@ joined_table:
n->larg = $1;
n->rarg = $3;
if ($4 != NULL && IsA($4, List))
- n->usingClause = (List *) $4; /* USING clause */
+ {
+ /* USING clause */
+ n->usingClause = linitial_node(List, castNode(List, $4));
+ n->join_using_alias = lsecond_node(Alias, castNode(List, $4));
+ }
else
- n->quals = $4; /* ON clause */
+ {
+ /* ON clause */
+ n->quals = $4;
+ }
$$ = n;
}
| table_ref NATURAL join_type JOIN table_ref
@@ -12135,6 +12150,7 @@ joined_table:
n->larg = $1;
n->rarg = $5;
n->usingClause = NIL; /* figure out which columns later... */
+ n->join_using_alias = NULL;
n->quals = NULL; /* fill later */
$$ = n;
}
@@ -12147,6 +12163,7 @@ joined_table:
n->larg = $1;
n->rarg = $4;
n->usingClause = NIL; /* figure out which columns later... */
+ n->join_using_alias = NULL;
n->quals = NULL; /* fill later */
$$ = n;
}
@@ -12181,6 +12198,22 @@ opt_alias_clause: alias_clause { $$ = $1; }
| /*EMPTY*/ { $$ = NULL; }
;
+/*
+ * The alias clause after JOIN ... USING only accepts the AS ColId spelling,
+ * per SQL standard. (The grammar could parse the other variants, but they
+ * don't seem to be useful, and it might lead to parser problems in the
+ * future.)
+ */
+opt_alias_clause_for_join_using:
+ AS ColId
+ {
+ $$ = makeNode(Alias);
+ $$->aliasname = $2;
+ /* the column name list will be inserted later */
+ }
+ | /*EMPTY*/ { $$ = NULL; }
+ ;
+
/*
* func_alias_clause can include both an Alias and a coldeflist, so we make it
* return a 2-element list that gets disassembled by calling production.
@@ -12225,15 +12258,24 @@ opt_outer: OUTER_P
/* JOIN qualification clauses
* Possibilities are:
- * USING ( column list ) allows only unqualified column names,
+ * USING ( column list ) [ AS alias ]
+ * allows only unqualified column names,
* which must match between tables.
* ON expr allows more general qualifications.
*
- * We return USING as a List node, while an ON-expr will not be a List.
+ * We return USING as a two-element List (the first item being a sub-List
+ * of the common column names, and the second either an Alias item or NULL).
+ * An ON-expr will not be a List, so it can be told apart that way.
*/
-join_qual: USING '(' name_list ')' { $$ = (Node *) $3; }
- | ON a_expr { $$ = $2; }
+join_qual: USING '(' name_list ')' opt_alias_clause_for_join_using
+ {
+ $$ = (Node *) list_make2($3, $5);
+ }
+ | ON a_expr
+ {
+ $$ = $2;
+ }
;
diff --git a/src/backend/parser/parse_clause.c b/src/backend/parser/parse_clause.c
index 5dfea46021..af80aa4593 100644
--- a/src/backend/parser/parse_clause.c
+++ b/src/backend/parser/parse_clause.c
@@ -1265,6 +1265,13 @@ transformFromClauseItem(ParseState *pstate, Node *n,
j->usingClause = rlist;
}
+ /*
+ * If a USING clause alias was specified, save the USING columns as
+ * its column list.
+ */
+ if (j->join_using_alias)
+ j->join_using_alias->colnames = j->usingClause;
+
/*
* Now transform the join qualifications, if any.
*/
@@ -1460,6 +1467,7 @@ transformFromClauseItem(ParseState *pstate, Node *n,
res_colvars,
l_colnos,
r_colnos,
+ j->join_using_alias,
j->alias,
true);
@@ -1493,6 +1501,30 @@ transformFromClauseItem(ParseState *pstate, Node *n,
pstate->p_joinexprs = lappend(pstate->p_joinexprs, j);
Assert(list_length(pstate->p_joinexprs) == j->rtindex);
+ /*
+ * If the join has a USING alias, build a ParseNamespaceItem for that
+ * and add it to the list of nsitems in the join's input.
+ */
+ if (j->join_using_alias)
+ {
+ ParseNamespaceItem *jnsitem;
+
+ jnsitem = (ParseNamespaceItem *) palloc(sizeof(ParseNamespaceItem));
+ jnsitem->p_names = j->join_using_alias;
+ jnsitem->p_rte = nsitem->p_rte;
+ jnsitem->p_rtindex = nsitem->p_rtindex;
+ /* no need to copy the first N columns, just use res_nscolumns */
+ jnsitem->p_nscolumns = res_nscolumns;
+ /* set default visibility flags; might get changed later */
+ jnsitem->p_rel_visible = true;
+ jnsitem->p_cols_visible = true;
+ jnsitem->p_lateral_only = false;
+ jnsitem->p_lateral_ok = true;
+ /* Per SQL, we must check for alias conflicts */
+ checkNameSpaceConflicts(pstate, list_make1(jnsitem), my_namespace);
+ my_namespace = lappend(my_namespace, jnsitem);
+ }
+
/*
* Prepare returned namespace list. If the JOIN has an alias then it
* hides the contained RTEs completely; otherwise, the contained RTEs
diff --git a/src/backend/parser/parse_expr.c b/src/backend/parser/parse_expr.c
index b38d919621..982244ee30 100644
--- a/src/backend/parser/parse_expr.c
+++ b/src/backend/parser/parse_expr.c
@@ -2508,27 +2508,61 @@ static Node *
transformWholeRowRef(ParseState *pstate, ParseNamespaceItem *nsitem,
int sublevels_up, int location)
{
- Var *result;
-
/*
- * Build the appropriate referencing node. Note that if the RTE is a
- * function returning scalar, we create just a plain reference to the
- * function value, not a composite containing a single column. This is
- * pretty inconsistent at first sight, but it's what we've done
- * historically. One argument for it is that "rel" and "rel.*" mean the
- * same thing for composite relations, so why not for scalar functions...
+ * Build the appropriate referencing node. Normally this can be a
+ * whole-row Var, but if the nsitem is a JOIN USING alias then it contains
+ * only a subset of the columns of the underlying join RTE, so that will
+ * not work. Instead we immediately expand the reference into a RowExpr.
+ * Since the JOIN USING's common columns are fully determined at this
+ * point, there seems no harm in expanding it now rather than during
+ * planning.
+ *
+ * Note that if the RTE is a function returning scalar, we create just a
+ * plain reference to the function value, not a composite containing a
+ * single column. This is pretty inconsistent at first sight, but it's
+ * what we've done historically. One argument for it is that "rel" and
+ * "rel.*" mean the same thing for composite relations, so why not for
+ * scalar functions...
*/
- /* XXX wrong for join alias case! */
- result = makeWholeRowVar(nsitem->p_rte, nsitem->p_rtindex,
- sublevels_up, true);
+ if (nsitem->p_names == nsitem->p_rte->eref)
+ {
+ Var *result;
- /* location is not filled in by makeWholeRowVar */
- result->location = location;
+ result = makeWholeRowVar(nsitem->p_rte, nsitem->p_rtindex,
+ sublevels_up, true);
- /* mark relation as requiring whole-row SELECT access */
- markVarForSelectPriv(pstate, result);
+ /* location is not filled in by makeWholeRowVar */
+ result->location = location;
- return (Node *) result;
+ /* mark relation as requiring whole-row SELECT access */
+ markVarForSelectPriv(pstate, result);
+
+ return (Node *) result;
+ }
+ else
+ {
+ RowExpr *rowexpr;
+ List *fields;
+
+ /*
+ * We want only as many columns as are listed in p_names->colnames,
+ * and we should use those names not whatever possibly-aliased names
+ * are in the RTE. We needn't worry about marking the RTE for SELECT
+ * access, as the common columns are surely so marked already.
+ */
+ expandRTE(nsitem->p_rte, nsitem->p_rtindex,
+ sublevels_up, location, false,
+ NULL, &fields);
+ rowexpr = makeNode(RowExpr);
+ rowexpr->args = list_truncate(fields,
+ list_length(nsitem->p_names->colnames));
+ rowexpr->row_typeid = RECORDOID;
+ rowexpr->row_format = COERCE_IMPLICIT_CAST;
+ rowexpr->colnames = copyObject(nsitem->p_names->colnames);
+ rowexpr->location = location;
+
+ return (Node *) rowexpr;
+ }
}
/*
diff --git a/src/backend/parser/parse_relation.c b/src/backend/parser/parse_relation.c
index 17232f027e..d451f055f7 100644
--- a/src/backend/parser/parse_relation.c
+++ b/src/backend/parser/parse_relation.c
@@ -2140,6 +2140,7 @@ addRangeTableEntryForJoin(ParseState *pstate,
List *aliasvars,
List *leftcols,
List *rightcols,
+ Alias *join_using_alias,
Alias *alias,
bool inFromCl)
{
@@ -2168,6 +2169,7 @@ addRangeTableEntryForJoin(ParseState *pstate,
rte->joinaliasvars = aliasvars;
rte->joinleftcols = leftcols;
rte->joinrightcols = rightcols;
+ rte->join_using_alias = join_using_alias;
rte->alias = alias;
eref = alias ? copyObject(alias) : makeAlias("unnamed_join", NIL);
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index f0de2a25c9..25db612c75 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -10644,6 +10644,10 @@ get_from_clause_item(Node *jtnode, Query *query, deparse_context *context)
appendStringInfoString(buf, quote_identifier(colname));
}
appendStringInfoChar(buf, ')');
+
+ if (j->join_using_alias)
+ appendStringInfo(buf, " AS %s",
+ quote_identifier(j->join_using_alias->aliasname));
}
else if (j->quals)
{
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 68425eb2c0..2364acd270 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -1068,6 +1068,13 @@ typedef struct RangeTblEntry
List *joinleftcols; /* left-side input column numbers */
List *joinrightcols; /* right-side input column numbers */
+ /*
+ * join_using_alias is an alias clause attached directly to JOIN/USING. It
+ * is different from the alias field (below) in that it does not hide the
+ * range variables of the tables being joined.
+ */
+ Alias *join_using_alias;
+
/*
* Fields valid for a function RTE (else NIL/zero):
*
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index d4ce037088..f66e1449d8 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -1499,6 +1499,11 @@ typedef struct RangeTblRef
* alias has a critical impact on semantics, because a join with an alias
* restricts visibility of the tables/columns inside it.
*
+ * join_using_alias is an Alias node representing the join correlation
+ * name that SQL:2016 and later allow to be attached to JOIN/USING.
+ * Its column alias list includes only the common column names from USING,
+ * and it does not restrict visibility of the join's input tables.
+ *
* During parse analysis, an RTE is created for the Join, and its index
* is filled into rtindex. This RTE is present mainly so that Vars can
* be created that refer to the outputs of the join. The planner sometimes
@@ -1514,6 +1519,7 @@ typedef struct JoinExpr
Node *larg; /* left subtree */
Node *rarg; /* right subtree */
List *usingClause; /* USING clause, if any (list of String) */
+ Alias *join_using_alias; /* alias attached to USING clause, if any */
Node *quals; /* qualifiers on join, if any */
Alias *alias; /* user-written alias clause, if any */
int rtindex; /* RT index assigned for join, or 0 */
diff --git a/src/include/parser/parse_relation.h b/src/include/parser/parse_relation.h
index 5dbe5ba2e2..8336c2c5a2 100644
--- a/src/include/parser/parse_relation.h
+++ b/src/include/parser/parse_relation.h
@@ -88,6 +88,7 @@ extern ParseNamespaceItem *addRangeTableEntryForJoin(ParseState *pstate,
List *aliasvars,
List *leftcols,
List *rightcols,
+ Alias *joinalias,
Alias *alias,
bool inFromCl);
extern ParseNamespaceItem *addRangeTableEntryForCTE(ParseState *pstate,
diff --git a/src/test/regress/expected/create_view.out b/src/test/regress/expected/create_view.out
index bd5fe60450..87fd2fbfd0 100644
--- a/src/test/regress/expected/create_view.out
+++ b/src/test/regress/expected/create_view.out
@@ -805,6 +805,51 @@ View definition:
(tbl3
CROSS JOIN tbl4) same;
+create table tbl1a (a int, c int);
+create view view_of_joins_2a as select * from tbl1 join tbl1a using (a);
+create view view_of_joins_2b as select * from tbl1 join tbl1a using (a) as x;
+create view view_of_joins_2c as select * from (tbl1 join tbl1a using (a)) as y;
+create view view_of_joins_2d as select * from (tbl1 join tbl1a using (a) as x) as y;
+select pg_get_viewdef('view_of_joins_2a', true);
+ pg_get_viewdef
+----------------------------
+ SELECT tbl1.a, +
+ tbl1.b, +
+ tbl1a.c +
+ FROM tbl1 +
+ JOIN tbl1a USING (a);
+(1 row)
+
+select pg_get_viewdef('view_of_joins_2b', true);
+ pg_get_viewdef
+---------------------------------
+ SELECT tbl1.a, +
+ tbl1.b, +
+ tbl1a.c +
+ FROM tbl1 +
+ JOIN tbl1a USING (a) AS x;
+(1 row)
+
+select pg_get_viewdef('view_of_joins_2c', true);
+ pg_get_viewdef
+-------------------------------
+ SELECT y.a, +
+ y.b, +
+ y.c +
+ FROM (tbl1 +
+ JOIN tbl1a USING (a)) y;
+(1 row)
+
+select pg_get_viewdef('view_of_joins_2d', true);
+ pg_get_viewdef
+------------------------------------
+ SELECT y.a, +
+ y.b, +
+ y.c +
+ FROM (tbl1 +
+ JOIN tbl1a USING (a) AS x) y;
+(1 row)
+
-- Test view decompilation in the face of column addition/deletion/renaming
create table tt2 (a int, b int, c int);
create table tt3 (ax int8, b int2, c numeric);
@@ -1949,7 +1994,7 @@ drop cascades to view aliased_view_2
drop cascades to view aliased_view_3
drop cascades to view aliased_view_4
DROP SCHEMA testviewschm2 CASCADE;
-NOTICE: drop cascades to 68 other objects
+NOTICE: drop cascades to 73 other objects
DETAIL: drop cascades to table t1
drop cascades to view temporal1
drop cascades to view temporal2
@@ -1974,6 +2019,11 @@ drop cascades to view unspecified_types
drop cascades to table tt1
drop cascades to table tx1
drop cascades to view view_of_joins
+drop cascades to table tbl1a
+drop cascades to view view_of_joins_2a
+drop cascades to view view_of_joins_2b
+drop cascades to view view_of_joins_2c
+drop cascades to view view_of_joins_2d
drop cascades to table tt2
drop cascades to table tt3
drop cascades to table tt4
diff --git a/src/test/regress/expected/join.out b/src/test/regress/expected/join.out
index 5c7528c029..8480e69204 100644
--- a/src/test/regress/expected/join.out
+++ b/src/test/regress/expected/join.out
@@ -1621,6 +1621,54 @@ SELECT *
4 | 1 | one | 2
(4 rows)
+-- test join using aliases
+SELECT * FROM J1_TBL JOIN J2_TBL USING (i) WHERE J1_TBL.t = 'one'; -- ok
+ i | j | t | k
+---+---+-----+----
+ 1 | 4 | one | -1
+(1 row)
+
+SELECT * FROM J1_TBL JOIN J2_TBL USING (i) AS x WHERE J1_TBL.t = 'one'; -- ok
+ i | j | t | k
+---+---+-----+----
+ 1 | 4 | one | -1
+(1 row)
+
+SELECT * FROM (J1_TBL JOIN J2_TBL USING (i)) AS x WHERE J1_TBL.t = 'one'; -- error
+ERROR: invalid reference to FROM-clause entry for table "j1_tbl"
+LINE 1: ... * FROM (J1_TBL JOIN J2_TBL USING (i)) AS x WHERE J1_TBL.t =...
+ ^
+HINT: There is an entry for table "j1_tbl", but it cannot be referenced from this part of the query.
+SELECT * FROM J1_TBL JOIN J2_TBL USING (i) AS x WHERE x.i = 1; -- ok
+ i | j | t | k
+---+---+-----+----
+ 1 | 4 | one | -1
+(1 row)
+
+SELECT * FROM J1_TBL JOIN J2_TBL USING (i) AS x WHERE x.t = 'one'; -- error
+ERROR: column x.t does not exist
+LINE 1: ...CT * FROM J1_TBL JOIN J2_TBL USING (i) AS x WHERE x.t = 'one...
+ ^
+SELECT * FROM J1_TBL a1 JOIN J2_TBL a2 USING (i) AS a1; -- error
+ERROR: table name "a1" specified more than once
+SELECT x.* FROM J1_TBL JOIN J2_TBL USING (i) AS x WHERE J1_TBL.t = 'one';
+ i
+---
+ 1
+(1 row)
+
+SELECT ROW(x.*) FROM J1_TBL JOIN J2_TBL USING (i) AS x WHERE J1_TBL.t = 'one';
+ row
+-----
+ (1)
+(1 row)
+
+SELECT row_to_json(x.*) FROM J1_TBL JOIN J2_TBL USING (i) AS x WHERE J1_TBL.t = 'one';
+ row_to_json
+-------------
+ {"i":1}
+(1 row)
+
--
-- NATURAL JOIN
-- Inner equi-join on all columns with the same name
diff --git a/src/test/regress/sql/create_view.sql b/src/test/regress/sql/create_view.sql
index fbd1313b9c..bdda56e8de 100644
--- a/src/test/regress/sql/create_view.sql
+++ b/src/test/regress/sql/create_view.sql
@@ -328,6 +328,17 @@ select * from
\d+ view_of_joins
+create table tbl1a (a int, c int);
+create view view_of_joins_2a as select * from tbl1 join tbl1a using (a);
+create view view_of_joins_2b as select * from tbl1 join tbl1a using (a) as x;
+create view view_of_joins_2c as select * from (tbl1 join tbl1a using (a)) as y;
+create view view_of_joins_2d as select * from (tbl1 join tbl1a using (a) as x) as y;
+
+select pg_get_viewdef('view_of_joins_2a', true);
+select pg_get_viewdef('view_of_joins_2b', true);
+select pg_get_viewdef('view_of_joins_2c', true);
+select pg_get_viewdef('view_of_joins_2d', true);
+
-- Test view decompilation in the face of column addition/deletion/renaming
create table tt2 (a int, b int, c int);
diff --git a/src/test/regress/sql/join.sql b/src/test/regress/sql/join.sql
index 6a209a27aa..5e7cc814f1 100644
--- a/src/test/regress/sql/join.sql
+++ b/src/test/regress/sql/join.sql
@@ -126,6 +126,16 @@ SELECT *
FROM J1_TBL t1 (a, b, c) JOIN J2_TBL t2 (a, b) USING (b)
ORDER BY b, t1.a;
+-- test join using aliases
+SELECT * FROM J1_TBL JOIN J2_TBL USING (i) WHERE J1_TBL.t = 'one'; -- ok
+SELECT * FROM J1_TBL JOIN J2_TBL USING (i) AS x WHERE J1_TBL.t = 'one'; -- ok
+SELECT * FROM (J1_TBL JOIN J2_TBL USING (i)) AS x WHERE J1_TBL.t = 'one'; -- error
+SELECT * FROM J1_TBL JOIN J2_TBL USING (i) AS x WHERE x.i = 1; -- ok
+SELECT * FROM J1_TBL JOIN J2_TBL USING (i) AS x WHERE x.t = 'one'; -- error
+SELECT * FROM J1_TBL a1 JOIN J2_TBL a2 USING (i) AS a1; -- error
+SELECT x.* FROM J1_TBL JOIN J2_TBL USING (i) AS x WHERE J1_TBL.t = 'one';
+SELECT ROW(x.*) FROM J1_TBL JOIN J2_TBL USING (i) AS x WHERE J1_TBL.t = 'one';
+SELECT row_to_json(x.*) FROM J1_TBL JOIN J2_TBL USING (i) AS x WHERE J1_TBL.t = 'one';
--
-- NATURAL JOIN
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