From: Tom Lane <tgl@sss.pgh.pa.us>
To: Erik Wienhold <ewie@ewie.name>
Cc: David G. Johnston <david.g.johnston@gmail.com>
Cc: Robert Haas <robertmhaas@gmail.com>
Cc: Hannu Krosing <hannuk@google.com>
Cc: Peter Eisentraut <peter@eisentraut.org>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: CREATE TABLE creates a composite type corresponding to the table row, which is and is not there
Date: Thu, 25 Jul 2024 16:29:11 -0400
Message-ID: <1556597.1721939351@sss.pgh.pa.us> (raw)
In-Reply-To: <1cd8a224-4038-43ba-bb11-a4cd8d015462@ewie.name>
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<CAKFQuwYcV+AZMbyzHyDdxFhp_GH5Nty_GL1U5JkPYJeya0MLYQ@mail.gmail.com>
<73jtqglviqor5ozqrthjmau7nj4xi7z4obzaqflf7cvliaf4em@4obr7wqlqkye>
<CAKFQuwYCqsapMBvQm9hTpD7urTaaOtJbpkpe7GaXr5ksMT58rA@mail.gmail.com>
<efxy4vnyrwhowyyv7vk6s7ps6bwkyizdmaehs7mppjzapssvxl@n5nuyelnyfcj>
<CA+TgmoZ4cUNV8BbMz6anMTsbcKkCQSs+V_ZWdCd5=2SB9pe67Q@mail.gmail.com>
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<e905f37d-7535-4df7-b171-ce1e569f4b40@ewie.name>
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<1cd8a224-4038-43ba-bb11-a4cd8d015462@ewie.name>
Erik Wienhold <ewie@ewie.name> writes:
> Thanks, I didn't know that guideline. Both fixed in v6.
This still isn't following our usual message style IMO. Here's a
proposed v7 that outputs
-ERROR: type stuff is not a composite type
+ERROR: type stuff is the row type of another table
+DETAIL: A typed table must use a stand-alone composite type created with CREATE TYPE.
I did a bit of copy-editing on the docs changes too. One notable
point is that I dropped the parenthetical bit about "(name optionally
schema-qualified)". That struck me as quite unnecessary, and
it definitely doesn't read well to have two parenthetical comments
in a single four-line sentence.
regards, tom lane
Attachments:v7-0001-Document-that-typed-tables-rely-on-CREATE-TYPE.patch (text/x-diff, 3.8K) downloaddiff --git a/doc/src/sgml/ref/create_table.sgml b/doc/src/sgml/ref/create_table.sgmlindex f19306e776..93b3f664f2 100644--- a/doc/src/sgml/ref/create_table.sgml+++ b/doc/src/sgml/ref/create_table.sgml@@ -249,18 +249,18 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
<listitem>
<para>
Creates a <firstterm>typed table</firstterm>, which takes its
- structure from the specified composite type (name optionally- schema-qualified). A typed table is tied to its type; for- example the table will be dropped if the type is dropped- (with <literal>DROP TYPE ... CASCADE</literal>).+ structure from the specified stand-alone composite type (that is,+ one created using <xref linkend="sql-createtype"/>) though it still+ produces a new composite type as well. The table will have a+ dependency on the referenced type, meaning that cascaded alter and+ drop actions on that type will propagate to the table.
</para>
<para>
- When a typed table is created, then the data types of the- columns are determined by the underlying composite type and are- not specified by the <literal>CREATE TABLE</literal> command.+ A typed table always has the same column names and data types as the+ type it is derived from, so you cannot specify additional columns.
But the <literal>CREATE TABLE</literal> command can add defaults
- and constraints to the table and can specify storage parameters.+ and constraints to the table, as well as specify storage parameters.
</para>
</listitem>
</varlistentry>
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.cindex 721d24783b..0b2a52463f 100644--- a/src/backend/commands/tablecmds.c+++ b/src/backend/commands/tablecmds.c@@ -6962,8 +6962,15 @@ check_of_type(HeapTuple typetuple)
* the type before the typed table creation/conversion commits.
*/
relation_close(typeRelation, NoLock);
++ if (!typeOk)+ ereport(ERROR,+ (errcode(ERRCODE_WRONG_OBJECT_TYPE),+ errmsg("type %s is the row type of another table",+ format_type_be(typ->oid)),+ errdetail("A typed table must use a stand-alone composite type created with CREATE TYPE.")));
}
- if (!typeOk)+ else
ereport(ERROR,
(errcode(ERRCODE_WRONG_OBJECT_TYPE),
errmsg("type %s is not a composite type",
diff --git a/src/test/regress/expected/typed_table.out b/src/test/regress/expected/typed_table.outindex 2e47ecbcf5..b6fbda3f21 100644--- a/src/test/regress/expected/typed_table.out+++ b/src/test/regress/expected/typed_table.out@@ -89,7 +89,12 @@ drop cascades to function get_all_persons()
drop cascades to table persons2
drop cascades to table persons3
CREATE TABLE persons5 OF stuff; -- only CREATE TYPE AS types may be used
-ERROR: type stuff is not a composite type+ERROR: type stuff is the row type of another table+DETAIL: A typed table must use a stand-alone composite type created with CREATE TYPE.+CREATE TYPE tt_enum_type AS ENUM ('a');+CREATE TABLE of_tt_enum_type OF tt_enum_type; -- not a composite type at all+ERROR: type tt_enum_type is not a composite type+DROP TYPE tt_enum_type;
DROP TABLE stuff;
-- implicit casting
CREATE TYPE person_type AS (id int, name text);
diff --git a/src/test/regress/sql/typed_table.sql b/src/test/regress/sql/typed_table.sqlindex 9ef0cdfcc7..57ce12782b 100644--- a/src/test/regress/sql/typed_table.sql+++ b/src/test/regress/sql/typed_table.sql@@ -48,6 +48,10 @@ DROP TYPE person_type CASCADE;
CREATE TABLE persons5 OF stuff; -- only CREATE TYPE AS types may be used
+CREATE TYPE tt_enum_type AS ENUM ('a');+CREATE TABLE of_tt_enum_type OF tt_enum_type; -- not a composite type at all+DROP TYPE tt_enum_type;+
DROP TABLE stuff;
=
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To: pgsql-hackers@postgresql.org
Cc: tgl@sss.pgh.pa.us, ewie@ewie.name, david.g.johnston@gmail.com, robertmhaas@gmail.com, hannuk@google.com, peter@eisentraut.org, pgsql-hackers@lists.postgresql.org
Subject: Re: CREATE TABLE creates a composite type corresponding to the table row, which is and is not there
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