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Improve error message and hint for ALTER COLUMN TYPE can't-cast failure.

2015年6月12日 15:54:03 +0000 (11:54 -0400)

We already tried to improve this once, but the "improved" text was rather
off-target if you had provided a USING clause. Also, it seems helpful
to provide the exact text of a suggested USING clause, so users can just
copy-and-paste it when needed. Per complaint from Keith Rarick and a
suggestion from Merlin Moncure.

Back-patch to 9.2 where the current wording was adopted.

src/backend/commands/tablecmds.c patch | blob | blame | history

src/test/regress/expected/alter_table.out patch | blob | blame | history

src/test/regress/sql/alter_table.sql patch | blob | blame | history

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c

index 84dbee0c41190e71cdf02473d143e5d88f11a3f9..d3947139c07d58276176ea421ca3e8ac3e8a764c 100644 (file)

--- a/src/backend/commands/tablecmds.c

+++ b/src/backend/commands/tablecmds.c

@@ -7888,11 +7888,26 @@ ATPrepAlterColumnType(List **wqueue,

COERCE_IMPLICIT_CAST,

-1);

if (transform == NULL)

- ereport(ERROR,

- (errcode(ERRCODE_DATATYPE_MISMATCH),

- errmsg("column \"%s\" cannot be cast automatically to type %s",

- colName, format_type_be(targettype)),

- errhint("Specify a USING expression to perform the conversion.")));

+ {

+ /* error text depends on whether USING was specified or not */

+ if (def->cooked_default != NULL)

+ ereport(ERROR,

+ (errcode(ERRCODE_DATATYPE_MISMATCH),

+ errmsg("result of USING clause for column \"%s\""

+ " cannot be cast automatically to type %s",

+ colName, format_type_be(targettype)),

+ errhint("You might need to add an explicit cast.")));

+ else

+ ereport(ERROR,

+ (errcode(ERRCODE_DATATYPE_MISMATCH),

+ errmsg("column \"%s\" cannot be cast automatically to type %s",

+ colName, format_type_be(targettype)),

+ /* translator: USING is SQL, don't translate it */

+ errhint("You might need to specify \"USING %s::%s\".",

+ quote_identifier(colName),

+ format_type_with_typemod(targettype,

+ targettypmod))));

+ }

/* Fix collations after all else */

assign_expr_collations(pstate, transform);

diff --git a/src/test/regress/expected/alter_table.out b/src/test/regress/expected/alter_table.out

index 65274bc26b71cf96a26f92ed08caf294ac1da13b..3ad2c55775c64e61e1f01f8929a04dfb95f5f1c3 100644 (file)

--- a/src/test/regress/expected/alter_table.out

+++ b/src/test/regress/expected/alter_table.out

@@ -1665,7 +1665,7 @@ select f3,max(f1) from foo group by f3;

-- Simple tests for alter table column type

alter table foo alter f1 TYPE integer; -- fails

ERROR: column "f1" cannot be cast automatically to type integer

-HINT: Specify a USING expression to perform the conversion.

+HINT: You might need to specify "USING f1::integer".

alter table foo alter f1 TYPE varchar(10);

create table anothertab (atcol1 serial8, atcol2 boolean,

constraint anothertab_chk check (atcol1 <= 3));

@@ -1680,7 +1680,10 @@ select * from anothertab;

alter table anothertab alter column atcol1 type boolean; -- fails

ERROR: column "atcol1" cannot be cast automatically to type boolean

-HINT: Specify a USING expression to perform the conversion.

+HINT: You might need to specify "USING atcol1::boolean".

+alter table anothertab alter column atcol1 type boolean using atcol1::int; -- fails

+ERROR: result of USING clause for column "atcol1" cannot be cast automatically to type boolean

+HINT: You might need to add an explicit cast.

alter table anothertab alter column atcol1 type integer;

select * from anothertab;

atcol1 | atcol2

diff --git a/src/test/regress/sql/alter_table.sql b/src/test/regress/sql/alter_table.sql

index b5ee7b087df8cc225f19c0a866558387ae156d9c..29c1875d2eaec34c58be594aa18fc65330e25828 100644 (file)

--- a/src/test/regress/sql/alter_table.sql

+++ b/src/test/regress/sql/alter_table.sql

@@ -1175,6 +1175,7 @@ insert into anothertab (atcol1, atcol2) values (default, false);

select * from anothertab;

alter table anothertab alter column atcol1 type boolean; -- fails

+alter table anothertab alter column atcol1 type boolean using atcol1::int; -- fails

alter table anothertab alter column atcol1 type integer;

select * from anothertab;

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