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Allow a multi-row INSERT to specify DEFAULTs for a generated column. 

One can say "INSERT INTO tab(generated_col) VALUES (DEFAULT)" and not
draw an error.  But the equivalent case for a multi-row VALUES list
always threw an error, even if one properly said DEFAULT in each row.
Fix that.  While here, improve the test cases for nearby logic about
OVERRIDING SYSTEM/USER values.

Dean Rasheed

Discussion: https://postgr.es/m/9q0sgcr416t.fsf@gmx.us
This commit is contained in:
Tom Lane 2020-11-22 15:48:32 -05:00
parent 9fe649ea29
commit 17958972fe
5 changed files with 357 additions and 32 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

242
src/backend/rewrite/rewriteHandler.c
View File

@ -69,13 +69,18 @@ static List *rewriteTargetListIU(List *targetList,
CmdType commandType,
OverridingKind override,
Relation target_relation,
int result_rti);
int result_rti,
RangeTblEntry *values_rte,
int values_rte_index,
Bitmapset **unused_values_attrnos);
static TargetEntry *process_matched_tle(TargetEntry *src_tle,
TargetEntry *prior_tle,
const char *attrName);
static Node *get_assignment_input(Node *node);
static Bitmapset *findDefaultOnlyColumns(RangeTblEntry *rte);
static bool rewriteValuesRTE(Query *parsetree, RangeTblEntry *rte, int rti,
Relation target_relation, bool force_nulls);
Relation target_relation, bool force_nulls,
Bitmapset *unused_cols);
static void markQueryForLocking(Query *qry, Node *jtnode,
LockClauseStrength strength, LockWaitPolicy waitPolicy,
bool pushedDown);
@ -708,13 +713,25 @@ adjustJoinTreeList(Query *parsetree, bool removert, int rt_index)
* is incorrect by this light, since child relations might have different
* column ordering, but the planner will fix things by re-sorting the tlist
* for each child.)
*
* If values_rte is non-NULL (i.e., we are doing a multi-row INSERT using
* values from a VALUES RTE), we populate *unused_values_attrnos with the
* attribute numbers of any unused columns from the VALUES RTE. This can
* happen for identity and generated columns whose targetlist entries are
* replaced with generated expressions (if INSERT ... OVERRIDING USER VALUE is
* used, or all the values to be inserted are DEFAULT). This information is
* required by rewriteValuesRTE() to handle any DEFAULT items in the unused
* columns. The caller must have initialized *unused_values_attrnos to NULL.
*/
static List *
rewriteTargetListIU(List *targetList,
CmdType commandType,
OverridingKind override,
Relation target_relation,
int result_rti)
int result_rti,
RangeTblEntry *values_rte,
int values_rte_index,
Bitmapset **unused_values_attrnos)
{
TargetEntry **new_tles;
List *new_tlist = NIL;
@ -724,6 +741,7 @@ rewriteTargetListIU(List *targetList,
next_junk_attrno,
numattrs;
ListCell *temp;
Bitmapset *default_only_cols = NULL;
/*
* We process the normal (non-junk) attributes by scanning the input tlist
@ -803,30 +821,106 @@ rewriteTargetListIU(List *targetList,
if (commandType == CMD_INSERT)
{
int values_attrno = 0;
/* Source attribute number for values that come from a VALUES RTE */
if (values_rte && new_tle && IsA(new_tle->expr, Var))
{
Var *var = (Var *) new_tle->expr;
if (var->varno == values_rte_index)
values_attrno = var->varattno;
}
/*
* Can only insert DEFAULT into GENERATED ALWAYS identity columns,
* unless either OVERRIDING USER VALUE or OVERRIDING SYSTEM VALUE
* is specified.
*/
if (att_tup->attidentity == ATTRIBUTE_IDENTITY_ALWAYS && !apply_default)
{
if (override == OVERRIDING_USER_VALUE)
apply_default = true;
else if (override != OVERRIDING_SYSTEM_VALUE)
ereport(ERROR,
(errcode(ERRCODE_GENERATED_ALWAYS),
errmsg("cannot insert into column \"%s\"", NameStr(att_tup->attname)),
errdetail("Column \"%s\" is an identity column defined as GENERATED ALWAYS.",
NameStr(att_tup->attname)),
errhint("Use OVERRIDING SYSTEM VALUE to override.")));
{
/*
* If this column's values come from a VALUES RTE, test
* whether it contains only SetToDefault items. Since the
* VALUES list might be quite large, we arrange to only
* scan it once.
*/
if (values_attrno != 0)
{
if (default_only_cols == NULL)
default_only_cols = findDefaultOnlyColumns(values_rte);
if (bms_is_member(values_attrno, default_only_cols))
apply_default = true;
}
if (!apply_default)
ereport(ERROR,
(errcode(ERRCODE_GENERATED_ALWAYS),
errmsg("cannot insert into column \"%s\"",
NameStr(att_tup->attname)),
errdetail("Column \"%s\" is an identity column defined as GENERATED ALWAYS.",
NameStr(att_tup->attname)),
errhint("Use OVERRIDING SYSTEM VALUE to override.")));
}
}
if (att_tup->attidentity == ATTRIBUTE_IDENTITY_BY_DEFAULT && override == OVERRIDING_USER_VALUE)
/*
* Although inserting into a GENERATED BY DEFAULT identity column
* is allowed, apply the default if OVERRIDING USER VALUE is
* specified.
*/
if (att_tup->attidentity == ATTRIBUTE_IDENTITY_BY_DEFAULT &&
override == OVERRIDING_USER_VALUE)
apply_default = true;
/*
* Can only insert DEFAULT into generated columns, regardless of
* any OVERRIDING clauses.
*/
if (att_tup->attgenerated && !apply_default)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("cannot insert into column \"%s\"", NameStr(att_tup->attname)),
errdetail("Column \"%s\" is a generated column.",
NameStr(att_tup->attname))));
{
/*
* If this column's values come from a VALUES RTE, test
* whether it contains only SetToDefault items, as above.
*/
if (values_attrno != 0)
{
if (default_only_cols == NULL)
default_only_cols = findDefaultOnlyColumns(values_rte);
if (bms_is_member(values_attrno, default_only_cols))
apply_default = true;
}
if (!apply_default)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("cannot insert into column \"%s\"",
NameStr(att_tup->attname)),
errdetail("Column \"%s\" is a generated column.",
NameStr(att_tup->attname))));
}
/*
* For an INSERT from a VALUES RTE, return the attribute numbers
* of any VALUES columns that will no longer be used (due to the
* targetlist entry being replaced by a default expression).
*/
if (values_attrno != 0 && apply_default && unused_values_attrnos)
*unused_values_attrnos = bms_add_member(*unused_values_attrnos,
values_attrno);
}
/*
* Updates to identity and generated columns follow the same rules as
* above, except that UPDATE doesn't admit OVERRIDING clauses. Also,
* the source can't be a VALUES RTE, so we needn't consider that.
*/
if (commandType == CMD_UPDATE)
{
if (att_tup->attidentity == ATTRIBUTE_IDENTITY_ALWAYS && new_tle && !apply_default)
@ -1219,6 +1313,62 @@ searchForDefault(RangeTblEntry *rte)
return false;
}
/*
* Search a VALUES RTE for columns that contain only SetToDefault items,
* returning a Bitmapset containing the attribute numbers of any such columns.
*/
static Bitmapset *
findDefaultOnlyColumns(RangeTblEntry *rte)
{
Bitmapset *default_only_cols = NULL;
ListCell *lc;
foreach(lc, rte->values_lists)
{
List *sublist = (List *) lfirst(lc);
ListCell *lc2;
int i;
if (default_only_cols == NULL)
{
/* Populate the initial result bitmap from the first row */
i = 0;
foreach(lc2, sublist)
{
Node *col = (Node *) lfirst(lc2);
i++;
if (IsA(col, SetToDefault))
default_only_cols = bms_add_member(default_only_cols, i);
}
}
else
{
/* Update the result bitmap from this next row */
i = 0;
foreach(lc2, sublist)
{
Node *col = (Node *) lfirst(lc2);
i++;
if (!IsA(col, SetToDefault))
default_only_cols = bms_del_member(default_only_cols, i);
}
}
/*
* If no column in the rows read so far contains only DEFAULT items,
* we are done.
*/
if (bms_is_empty(default_only_cols))
break;
}
return default_only_cols;
}
/*
* When processing INSERT ... VALUES with a VALUES RTE (ie, multiple VALUES
* lists), we have to replace any DEFAULT items in the VALUES lists with
@ -1246,19 +1396,31 @@ searchForDefault(RangeTblEntry *rte)
* an insert into an auto-updatable view, and the product queries are inserts
* into a rule-updatable view.
*
* Finally, if a DEFAULT item is found in a column mentioned in unused_cols,
* it is explicitly set to NULL. This happens for columns in the VALUES RTE
* whose corresponding targetlist entries have already been replaced with the
* relation's default expressions, so that any values in those columns of the
* VALUES RTE are no longer used. This can happen for identity and generated
* columns (if INSERT ... OVERRIDING USER VALUE is used, or all the values to
* be inserted are DEFAULT). In principle we could replace all entries in
* such a column with NULL, whether DEFAULT or not; but it doesn't seem worth
* the trouble.
*
* Note that we may have subscripted or field assignment targetlist entries,
* as well as more complex expressions from already-replaced DEFAULT items if
* we have recursed to here for an auto-updatable view. However, it ought to
* be impossible for such entries to have DEFAULTs assigned to them --- we
* should only have to replace DEFAULT items for targetlist entries that
* contain simple Vars referencing the VALUES RTE.
* be impossible for such entries to have DEFAULTs assigned to them, except
* for unused columns, as described above --- we should only have to replace
* DEFAULT items for targetlist entries that contain simple Vars referencing
* the VALUES RTE, or which are no longer referred to by the targetlist.
*
* Returns true if all DEFAULT items were replaced, and false if some were
* left untouched.
*/
static bool
rewriteValuesRTE(Query *parsetree, RangeTblEntry *rte, int rti,
Relation target_relation, bool force_nulls)
Relation target_relation, bool force_nulls,
Bitmapset *unused_cols)
{
List *newValues;
ListCell *lc;
@ -1282,8 +1444,8 @@ rewriteValuesRTE(Query *parsetree, RangeTblEntry *rte, int rti,
* Scan the targetlist for entries referring to the VALUES RTE, and note
* the target attributes. As noted above, we should only need to do this
* for targetlist entries containing simple Vars --- nothing else in the
* VALUES RTE should contain DEFAULT items, and we complain if such a
* thing does occur.
* VALUES RTE should contain DEFAULT items (except possibly for unused
* columns), and we complain if such a thing does occur.
*/
numattrs = list_length(linitial(rte->values_lists));
attrnos = (int *) palloc0(numattrs * sizeof(int));
@ -1370,6 +1532,22 @@ rewriteValuesRTE(Query *parsetree, RangeTblEntry *rte, int rti,
Form_pg_attribute att_tup;
Node *new_expr;
/*
* If this column isn't used, just replace the DEFAULT with
* NULL (attrno will be 0 in this case because the targetlist
* entry will have been replaced by the default expression).
*/
if (bms_is_member(i, unused_cols))
{
SetToDefault *def = (SetToDefault *) col;
newList = lappend(newList,
makeNullConst(def->typeId,
def->typeMod,
def->collation));
continue;
}
if (attrno == 0)
elog(ERROR, "cannot set value in column %d to DEFAULT", i);
att_tup = TupleDescAttr(target_relation->rd_att, attrno - 1);
@ -3614,15 +3792,21 @@ RewriteQuery(Query *parsetree, List *rewrite_events)
if (values_rte)
{
Bitmapset *unused_values_attrnos = NULL;
/* Process the main targetlist ... */
parsetree->targetList = rewriteTargetListIU(parsetree->targetList,
parsetree->commandType,
parsetree->override,
rt_entry_relation,
parsetree->resultRelation);
parsetree->resultRelation,
values_rte,
values_rte_index,
&unused_values_attrnos);
/* ... and the VALUES expression lists */
if (!rewriteValuesRTE(parsetree, values_rte, values_rte_index,
rt_entry_relation, false))
rt_entry_relation, false,
unused_values_attrnos))
defaults_remaining = true;
}
else
@ -3633,7 +3817,8 @@ RewriteQuery(Query *parsetree, List *rewrite_events)
parsetree->commandType,
parsetree->override,
rt_entry_relation,
parsetree->resultRelation);
parsetree->resultRelation,
NULL, 0, NULL);
}
if (parsetree->onConflict &&
@ -3644,7 +3829,8 @@ RewriteQuery(Query *parsetree, List *rewrite_events)
CMD_UPDATE,
parsetree->override,
rt_entry_relation,
parsetree->resultRelation);
parsetree->resultRelation,
NULL, 0, NULL);
}
}
else if (event == CMD_UPDATE)
@ -3654,7 +3840,8 @@ RewriteQuery(Query *parsetree, List *rewrite_events)
parsetree->commandType,
parsetree->override,
rt_entry_relation,
parsetree->resultRelation);
parsetree->resultRelation,
NULL, 0, NULL);
/* Also populate extraUpdatedCols (for generated columns) */
fill_extraUpdatedCols(rt_entry, rt_entry_relation);
@ -3704,7 +3891,8 @@ RewriteQuery(Query *parsetree, List *rewrite_events)
rewriteValuesRTE(pt, values_rte, values_rte_index,
rt_entry_relation,
true); /* Force remaining defaults to NULL */
true, /* Force remaining defaults to NULL */
NULL);
}
}

47
src/test/regress/expected/generated.out
View File

@ -91,17 +91,30 @@ ERROR: for a generated column, GENERATED ALWAYS must be specified
LINE 1: ...E gtest_err_8 (a int PRIMARY KEY, b int GENERATED BY DEFAULT...
^
INSERT INTO gtest1 VALUES (1);
INSERT INTO gtest1 VALUES (2, DEFAULT);
INSERT INTO gtest1 VALUES (2, DEFAULT); -- ok
INSERT INTO gtest1 VALUES (3, 33); -- error
ERROR: cannot insert into column "b"
DETAIL: Column "b" is a generated column.
INSERT INTO gtest1 VALUES (3, 33), (4, 44); -- error
ERROR: cannot insert into column "b"
DETAIL: Column "b" is a generated column.
INSERT INTO gtest1 VALUES (3, DEFAULT), (4, 44); -- error
ERROR: cannot insert into column "b"
DETAIL: Column "b" is a generated column.
INSERT INTO gtest1 VALUES (3, 33), (4, DEFAULT); -- error
ERROR: cannot insert into column "b"
DETAIL: Column "b" is a generated column.
INSERT INTO gtest1 VALUES (3, DEFAULT), (4, DEFAULT); -- ok
SELECT * FROM gtest1 ORDER BY a;
a | b
---+---
1 | 2
2 | 4
(2 rows)
3 | 6
4 | 8
(4 rows)
DELETE FROM gtest1 WHERE a >= 3;
UPDATE gtest1 SET b = DEFAULT WHERE a = 1;
UPDATE gtest1 SET b = 11 WHERE a = 1; -- error
ERROR: column "b" can only be updated to DEFAULT
@ -179,9 +192,37 @@ SELECT * FROM gtest1v;
3 | 6
(1 row)
INSERT INTO gtest1v VALUES (4, 8); -- fails
INSERT INTO gtest1v VALUES (4, 8); -- error
ERROR: cannot insert into column "b"
DETAIL: Column "b" is a generated column.
INSERT INTO gtest1v VALUES (5, DEFAULT); -- ok
INSERT INTO gtest1v VALUES (6, 66), (7, 77); -- error
ERROR: cannot insert into column "b"
DETAIL: Column "b" is a generated column.
INSERT INTO gtest1v VALUES (6, DEFAULT), (7, 77); -- error
ERROR: cannot insert into column "b"
DETAIL: Column "b" is a generated column.
INSERT INTO gtest1v VALUES (6, 66), (7, DEFAULT); -- error
ERROR: cannot insert into column "b"
DETAIL: Column "b" is a generated column.
INSERT INTO gtest1v VALUES (6, DEFAULT), (7, DEFAULT); -- ok
ALTER VIEW gtest1v ALTER COLUMN b SET DEFAULT 100;
INSERT INTO gtest1v VALUES (8, DEFAULT); -- error
ERROR: cannot insert into column "b"
DETAIL: Column "b" is a generated column.
INSERT INTO gtest1v VALUES (8, DEFAULT), (9, DEFAULT); -- error
ERROR: cannot insert into column "b"
DETAIL: Column "b" is a generated column.
SELECT * FROM gtest1v;
a | b
---+----
3 | 6
5 | 10
6 | 12
7 | 14
(4 rows)
DELETE FROM gtest1v WHERE a >= 5;
DROP VIEW gtest1v;
-- CTEs
WITH foo AS (SELECT * FROM gtest1) SELECT * FROM foo;

56
src/test/regress/expected/identity.out
View File

@ -105,6 +105,62 @@ SELECT * FROM itest4;
(2 rows)
-- VALUES RTEs
CREATE TABLE itest5 (a int generated always as identity, b text);
INSERT INTO itest5 VALUES (1, 'a'); -- error
ERROR: cannot insert into column "a"
DETAIL: Column "a" is an identity column defined as GENERATED ALWAYS.
HINT: Use OVERRIDING SYSTEM VALUE to override.
INSERT INTO itest5 VALUES (DEFAULT, 'a'); -- ok
INSERT INTO itest5 VALUES (2, 'b'), (3, 'c'); -- error
ERROR: cannot insert into column "a"
DETAIL: Column "a" is an identity column defined as GENERATED ALWAYS.
HINT: Use OVERRIDING SYSTEM VALUE to override.
INSERT INTO itest5 VALUES (DEFAULT, 'b'), (3, 'c'); -- error
ERROR: cannot insert into column "a"
DETAIL: Column "a" is an identity column defined as GENERATED ALWAYS.
HINT: Use OVERRIDING SYSTEM VALUE to override.
INSERT INTO itest5 VALUES (2, 'b'), (DEFAULT, 'c'); -- error
ERROR: cannot insert into column "a"
DETAIL: Column "a" is an identity column defined as GENERATED ALWAYS.
HINT: Use OVERRIDING SYSTEM VALUE to override.
INSERT INTO itest5 VALUES (DEFAULT, 'b'), (DEFAULT, 'c'); -- ok
INSERT INTO itest5 OVERRIDING SYSTEM VALUE VALUES (-1, 'aa');
INSERT INTO itest5 OVERRIDING SYSTEM VALUE VALUES (-2, 'bb'), (-3, 'cc');
INSERT INTO itest5 OVERRIDING SYSTEM VALUE VALUES (DEFAULT, 'dd'), (-4, 'ee');
INSERT INTO itest5 OVERRIDING SYSTEM VALUE VALUES (-5, 'ff'), (DEFAULT, 'gg');
INSERT INTO itest5 OVERRIDING SYSTEM VALUE VALUES (DEFAULT, 'hh'), (DEFAULT, 'ii');
INSERT INTO itest5 OVERRIDING USER VALUE VALUES (-1, 'aaa');
INSERT INTO itest5 OVERRIDING USER VALUE VALUES (-2, 'bbb'), (-3, 'ccc');
INSERT INTO itest5 OVERRIDING USER VALUE VALUES (DEFAULT, 'ddd'), (-4, 'eee');
INSERT INTO itest5 OVERRIDING USER VALUE VALUES (-5, 'fff'), (DEFAULT, 'ggg');
INSERT INTO itest5 OVERRIDING USER VALUE VALUES (DEFAULT, 'hhh'), (DEFAULT, 'iii');
SELECT * FROM itest5;
a | b
----+-----
1 | a
2 | b
3 | c
-1 | aa
-2 | bb
-3 | cc
4 | dd
-4 | ee
-5 | ff
5 | gg
6 | hh
7 | ii
8 | aaa
9 | bbb
10 | ccc
11 | ddd
12 | eee
13 | fff
14 | ggg
15 | hhh
16 | iii
(21 rows)
DROP TABLE itest5;
INSERT INTO itest3 VALUES (DEFAULT, 'a');
INSERT INTO itest3 VALUES (DEFAULT, 'b'), (DEFAULT, 'c');
SELECT * FROM itest3;

21
src/test/regress/sql/generated.sql
View File

@ -41,10 +41,15 @@ CREATE TABLE gtest_err_7d (a int PRIMARY KEY, b int GENERATED ALWAYS AS (generat
CREATE TABLE gtest_err_8 (a int PRIMARY KEY, b int GENERATED BY DEFAULT AS (a * 2) STORED);
INSERT INTO gtest1 VALUES (1);
INSERT INTO gtest1 VALUES (2, DEFAULT);
INSERT INTO gtest1 VALUES (2, DEFAULT); -- ok
INSERT INTO gtest1 VALUES (3, 33); -- error
INSERT INTO gtest1 VALUES (3, 33), (4, 44); -- error
INSERT INTO gtest1 VALUES (3, DEFAULT), (4, 44); -- error
INSERT INTO gtest1 VALUES (3, 33), (4, DEFAULT); -- error
INSERT INTO gtest1 VALUES (3, DEFAULT), (4, DEFAULT); -- ok
SELECT * FROM gtest1 ORDER BY a;
DELETE FROM gtest1 WHERE a >= 3;
UPDATE gtest1 SET b = DEFAULT WHERE a = 1;
UPDATE gtest1 SET b = 11 WHERE a = 1; -- error
@ -75,7 +80,19 @@ SELECT * FROM gtest1 ORDER BY a;
-- views
CREATE VIEW gtest1v AS SELECT * FROM gtest1;
SELECT * FROM gtest1v;
INSERT INTO gtest1v VALUES (4, 8); -- fails
INSERT INTO gtest1v VALUES (4, 8); -- error
INSERT INTO gtest1v VALUES (5, DEFAULT); -- ok
INSERT INTO gtest1v VALUES (6, 66), (7, 77); -- error
INSERT INTO gtest1v VALUES (6, DEFAULT), (7, 77); -- error
INSERT INTO gtest1v VALUES (6, 66), (7, DEFAULT); -- error
INSERT INTO gtest1v VALUES (6, DEFAULT), (7, DEFAULT); -- ok
ALTER VIEW gtest1v ALTER COLUMN b SET DEFAULT 100;
INSERT INTO gtest1v VALUES (8, DEFAULT); -- error
INSERT INTO gtest1v VALUES (8, DEFAULT), (9, DEFAULT); -- error
SELECT * FROM gtest1v;
DELETE FROM gtest1v WHERE a >= 5;
DROP VIEW gtest1v;
-- CTEs

23
src/test/regress/sql/identity.sql
View File

@ -56,6 +56,29 @@ SELECT * FROM itest4;
-- VALUES RTEs
CREATE TABLE itest5 (a int generated always as identity, b text);
INSERT INTO itest5 VALUES (1, 'a'); -- error
INSERT INTO itest5 VALUES (DEFAULT, 'a'); -- ok
INSERT INTO itest5 VALUES (2, 'b'), (3, 'c'); -- error
INSERT INTO itest5 VALUES (DEFAULT, 'b'), (3, 'c'); -- error
INSERT INTO itest5 VALUES (2, 'b'), (DEFAULT, 'c'); -- error
INSERT INTO itest5 VALUES (DEFAULT, 'b'), (DEFAULT, 'c'); -- ok
INSERT INTO itest5 OVERRIDING SYSTEM VALUE VALUES (-1, 'aa');
INSERT INTO itest5 OVERRIDING SYSTEM VALUE VALUES (-2, 'bb'), (-3, 'cc');
INSERT INTO itest5 OVERRIDING SYSTEM VALUE VALUES (DEFAULT, 'dd'), (-4, 'ee');
INSERT INTO itest5 OVERRIDING SYSTEM VALUE VALUES (-5, 'ff'), (DEFAULT, 'gg');
INSERT INTO itest5 OVERRIDING SYSTEM VALUE VALUES (DEFAULT, 'hh'), (DEFAULT, 'ii');
INSERT INTO itest5 OVERRIDING USER VALUE VALUES (-1, 'aaa');
INSERT INTO itest5 OVERRIDING USER VALUE VALUES (-2, 'bbb'), (-3, 'ccc');
INSERT INTO itest5 OVERRIDING USER VALUE VALUES (DEFAULT, 'ddd'), (-4, 'eee');
INSERT INTO itest5 OVERRIDING USER VALUE VALUES (-5, 'fff'), (DEFAULT, 'ggg');
INSERT INTO itest5 OVERRIDING USER VALUE VALUES (DEFAULT, 'hhh'), (DEFAULT, 'iii');
SELECT * FROM itest5;
DROP TABLE itest5;
INSERT INTO itest3 VALUES (DEFAULT, 'a');
INSERT INTO itest3 VALUES (DEFAULT, 'b'), (DEFAULT, 'c');