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Commitd6f96ed

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Allow specifying column list for foreign key ON DELETE SET actions
Extend the foreign key ON DELETE actions SET NULL and SET DEFAULT byallowing the specification of a column list, like CREATE TABLE posts ( ... FOREIGN KEY (tenant_id, author_id) REFERENCES users ON DELETE SET NULL (author_id) );If a column list is specified, only those columns are set tonull/default, instead of all the columns in the foreign-keyconstraint.This is useful for multitenant or sharded schemas, where the tenant orshard ID is included in the primary key of all tables but shouldn't beset to null.Author: Paul Martinez <paulmtz@google.com>Discussion:https://www.postgresql.org/message-id/flat/CACqFVBZQyMYJV=njbSMxf+rbDHpx=W=B7AEaMKn8dWn9OZJY7w@mail.gmail.com
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22 files changed

+557
-72
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22 files changed

+557
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‎doc/src/sgml/catalogs.sgml‎

Lines changed: 12 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -2708,6 +2708,18 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
27082708
</para></entry>
27092709
</row>
27102710

2711+
<row>
2712+
<entry role="catalog_table_entry"><para role="column_definition">
2713+
<structfield>confdelsetcols</structfield> <type>int2[]</type>
2714+
(references <link linkend="catalog-pg-attribute"><structname>pg_attribute</structname></link>.<structfield>attnum</structfield>)
2715+
</para>
2716+
<para>
2717+
If a foreign key with a <literal>SET NULL</literal> or <literal>SET
2718+
DEFAULT</literal> delete action, the columns that will be updated.
2719+
If null, all of the referencing columns will be updated.
2720+
</para></entry>
2721+
</row>
2722+
27112723
<row>
27122724
<entry role="catalog_table_entry"><para role="column_definition">
27132725
<structfield>conexclop</structfield> <type>oid[]</type>

‎doc/src/sgml/ddl.sgml‎

Lines changed: 32 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1083,10 +1083,41 @@ CREATE TABLE order_items (
10831083
manager to null or a default might be useful.
10841084
</para>
10851085

1086+
<para>
1087+
The actions <literal>SET NULL</literal> and <literal>SET DEFAULT</literal>
1088+
can take a column list to specify which columns to set. Normally, all
1089+
columns of the foreign-key constraint are set; setting only a subset is
1090+
useful in some special cases. Consider the following example:
1091+
<programlisting>
1092+
CREATE TABLE tenants (
1093+
tenant_id integer PRIMARY KEY
1094+
);
1095+
1096+
CREATE TABLE users (
1097+
tenant_id integer REFERENCES tenants ON DELETE CASCADE,
1098+
user_id integer NOT NULL,
1099+
PRIMARY KEY (tenant_id, user_id)
1100+
);
1101+
1102+
CREATE TABLE posts (
1103+
tenant_id integer REFERENCES tenants ON DELETE CASCADE,
1104+
post_id integer NOT NULL,
1105+
author_id integer,
1106+
PRIMARY KEY (tenant_id, post_id),
1107+
FOREIGN KEY (tenant_id, author_id) REFERENCES users ON DELETE SET NULL <emphasis>(author_id)</emphasis>
1108+
);
1109+
</programlisting>
1110+
Without the specification of the column, the foreign key would also set
1111+
the column <literal>tenant_id</literal> to null, but that column is still
1112+
required as part of the primary key.
1113+
</para>
1114+
10861115
<para>
10871116
Analogous to <literal>ON DELETE</literal> there is also
10881117
<literal>ON UPDATE</literal> which is invoked when a referenced
1089-
column is changed (updated). The possible actions are the same.
1118+
column is changed (updated). The possible actions are the same,
1119+
except that column lists cannot be specified for <literal>SET
1120+
NULL</literal> and <literal>SET DEFAULT</literal>.
10901121
In this case, <literal>CASCADE</literal> means that the updated values of the
10911122
referenced column(s) should be copied into the referencing row(s).
10921123
</para>

‎doc/src/sgml/ref/alter_table.sgml‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -138,7 +138,7 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
138138

139139
<phrase><replaceable class="parameter">referential_action</replaceable> in a <literal>FOREIGN KEY</literal>/<literal>REFERENCES</literal> constraint is:</phrase>
140140

141-
{ NO ACTION | RESTRICT | CASCADE | SET NULL | SET DEFAULT }
141+
{ NO ACTION | RESTRICT | CASCADE | SET NULL[ ( <replaceable class="parameter">column_name</replaceable> [, ... ] ) ]| SET DEFAULT [ ( <replaceable class="parameter">column_name</replaceable> [, ... ] ) ] }
142142
</synopsis>
143143
</refsynopsisdiv>
144144

‎doc/src/sgml/ref/create_table.sgml‎

Lines changed: 19 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -108,7 +108,7 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
108108

109109
<phrase><replaceable class="parameter">referential_action</replaceable> in a <literal>FOREIGN KEY</literal>/<literal>REFERENCES</literal> constraint is:</phrase>
110110

111-
{ NO ACTION | RESTRICT | CASCADE | SET NULL | SET DEFAULT }
111+
{ NO ACTION | RESTRICT | CASCADE | SET NULL[ ( <replaceable class="parameter">column_name</replaceable> [, ... ] ) ]| SET DEFAULT [ ( <replaceable class="parameter">column_name</replaceable> [, ... ] ) ] }
112112
</synopsis>
113113

114114
</refsynopsisdiv>
@@ -1169,19 +1169,23 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
11691169
</varlistentry>
11701170

11711171
<varlistentry>
1172-
<term><literal>SET NULL</literal></term>
1172+
<term><literal>SET NULL [ ( <replaceable>column_name</replaceable> [, ... ] ) ]</literal></term>
11731173
<listitem>
11741174
<para>
1175-
Set the referencing column(s) to null.
1175+
Set all of the referencing columns, or a specified subset of the
1176+
referencing columns, to null. A subset of columns can only be
1177+
specified for <literal>ON DELETE</literal> actions.
11761178
</para>
11771179
</listitem>
11781180
</varlistentry>
11791181

11801182
<varlistentry>
1181-
<term><literal>SET DEFAULT</literal></term>
1183+
<term><literal>SET DEFAULT [ ( <replaceable>column_name</replaceable> [, ... ] ) ]</literal></term>
11821184
<listitem>
11831185
<para>
1184-
Set the referencing column(s) to their default values.
1186+
Set all of the referencing columns, or a specified subset of the
1187+
referencing columns, to their default values. A subset of columns
1188+
can only be specified for <literal>ON DELETE</literal> actions.
11851189
(There must be a row in the referenced table matching the default
11861190
values, if they are not null, or the operation will fail.)
11871191
</para>
@@ -2223,6 +2227,16 @@ CREATE TABLE cities_partdef
22232227
</para>
22242228
</refsect2>
22252229

2230+
<refsect2>
2231+
<title>Foreign-Key Constraint Actions</title>
2232+
2233+
<para>
2234+
The ability to specify column lists in the foreign-key actions
2235+
<literal>SET DEFAULT</literal> and <literal>SET NULL</literal> is a
2236+
<productname>PostgreSQL</productname> extension.
2237+
</para>
2238+
</refsect2>
2239+
22262240
<refsect2>
22272241
<title><literal>NULL</literal> <quote>Constraint</quote></title>
22282242

‎src/backend/catalog/heap.c‎

Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -2441,6 +2441,8 @@ StoreRelCheck(Relation rel, const char *ccname, Node *expr,
24412441
0,
24422442
' ',
24432443
' ',
2444+
NULL,
2445+
0,
24442446
' ',
24452447
NULL,/* not an exclusion constraint */
24462448
expr,/* Tree form of check constraint */

‎src/backend/catalog/index.c‎

Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1969,6 +1969,8 @@ index_constraint_create(Relation heapRelation,
19691969
0,
19701970
' ',
19711971
' ',
1972+
NULL,
1973+
0,
19721974
' ',
19731975
indexInfo->ii_ExclusionOps,
19741976
NULL,/* no check constraint */

‎src/backend/catalog/pg_constraint.c‎

Lines changed: 50 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -68,6 +68,8 @@ CreateConstraintEntry(const char *constraintName,
6868
intforeignNKeys,
6969
charforeignUpdateType,
7070
charforeignDeleteType,
71+
constint16*fkDeleteSetCols,
72+
intnumFkDeleteSetCols,
7173
charforeignMatchType,
7274
constOid*exclOp,
7375
Node*conExpr,
@@ -88,6 +90,7 @@ CreateConstraintEntry(const char *constraintName,
8890
ArrayType*conppeqopArray;
8991
ArrayType*conffeqopArray;
9092
ArrayType*conexclopArray;
93+
ArrayType*confdelsetcolsArray;
9194
NameDatacname;
9295
inti;
9396
ObjectAddressconobject;
@@ -136,13 +139,24 @@ CreateConstraintEntry(const char *constraintName,
136139
fkdatums[i]=ObjectIdGetDatum(ffEqOp[i]);
137140
conffeqopArray=construct_array(fkdatums,foreignNKeys,
138141
OIDOID,sizeof(Oid), true,TYPALIGN_INT);
142+
143+
if (numFkDeleteSetCols>0)
144+
{
145+
for (i=0;i<numFkDeleteSetCols;i++)
146+
fkdatums[i]=Int16GetDatum(fkDeleteSetCols[i]);
147+
confdelsetcolsArray=construct_array(fkdatums,numFkDeleteSetCols,
148+
INT2OID,2, true,TYPALIGN_SHORT);
149+
}
150+
else
151+
confdelsetcolsArray=NULL;
139152
}
140153
else
141154
{
142155
confkeyArray=NULL;
143156
conpfeqopArray=NULL;
144157
conppeqopArray=NULL;
145158
conffeqopArray=NULL;
159+
confdelsetcolsArray=NULL;
146160
}
147161

148162
if (exclOp!=NULL)
@@ -211,6 +225,11 @@ CreateConstraintEntry(const char *constraintName,
211225
else
212226
nulls[Anum_pg_constraint_conffeqop-1]= true;
213227

228+
if (confdelsetcolsArray)
229+
values[Anum_pg_constraint_confdelsetcols-1]=PointerGetDatum(confdelsetcolsArray);
230+
else
231+
nulls[Anum_pg_constraint_confdelsetcols-1]= true;
232+
214233
if (conexclopArray)
215234
values[Anum_pg_constraint_conexclop-1]=PointerGetDatum(conexclopArray);
216235
else
@@ -1157,13 +1176,15 @@ get_primary_key_attnos(Oid relid, bool deferrableOk, Oid *constraintOid)
11571176
/*
11581177
* Extract data from the pg_constraint tuple of a foreign-key constraint.
11591178
*
1160-
* All arguments save the first are output arguments; the last three of them
1161-
* can be passed as NULL if caller doesn't need them.
1179+
* All arguments save the first are output arguments. All output arguments
1180+
* other than numfks, conkey and confkey can be passed as NULL if caller
1181+
* doesn't need them.
11621182
*/
11631183
void
11641184
DeconstructFkConstraintRow(HeapTupletuple,int*numfks,
11651185
AttrNumber*conkey,AttrNumber*confkey,
1166-
Oid*pf_eq_oprs,Oid*pp_eq_oprs,Oid*ff_eq_oprs)
1186+
Oid*pf_eq_oprs,Oid*pp_eq_oprs,Oid*ff_eq_oprs,
1187+
int*num_fk_del_set_cols,AttrNumber*fk_del_set_cols)
11671188
{
11681189
OidconstrId;
11691190
Datumadatum;
@@ -1260,6 +1281,32 @@ DeconstructFkConstraintRow(HeapTuple tuple, int *numfks,
12601281
pfree(arr);/* free de-toasted copy, if any */
12611282
}
12621283

1284+
if (fk_del_set_cols)
1285+
{
1286+
adatum=SysCacheGetAttr(CONSTROID,tuple,
1287+
Anum_pg_constraint_confdelsetcols,&isNull);
1288+
if (isNull)
1289+
{
1290+
*num_fk_del_set_cols=0;
1291+
}
1292+
else
1293+
{
1294+
intnum_delete_cols;
1295+
1296+
arr=DatumGetArrayTypeP(adatum);/* ensure not toasted */
1297+
if (ARR_NDIM(arr)!=1||
1298+
ARR_HASNULL(arr)||
1299+
ARR_ELEMTYPE(arr)!=INT2OID)
1300+
elog(ERROR,"confdelsetcols is not a 1-D smallint array");
1301+
num_delete_cols=ARR_DIMS(arr)[0];
1302+
memcpy(fk_del_set_cols,ARR_DATA_PTR(arr),num_delete_cols*sizeof(int16));
1303+
if ((Pointer)arr!=DatumGetPointer(adatum))
1304+
pfree(arr);/* free de-toasted copy, if any */
1305+
1306+
*num_fk_del_set_cols=num_delete_cols;
1307+
}
1308+
}
1309+
12631310
*numfks=numkeys;
12641311
}
12651312

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