Thread: SQL Spec Compliance Questions
Folks, Just got this "do we support it" questionnaire from a signficant commercial entity vaguely interested in supporting PostrgreSQL. Since I'm often foggy on the differences between the SQL99 and SQL92 spec definitions of things, I thought I'd post it for feedback here: 1) SQL-92 SELECT, INSERT, UPDATE, DELETE 2) SQL-92 CREATE/DROP SCHEMA/TABLE 3) SQL-92 INFORMATION_SCHEMA or SQL/CLI or ODBC driver with metadata functions 4) SQL-99 CREATE TRIGGER/DROP TRIGGER 5) SQL-99 BLOB, CLOB Data Types up to 1MB 6) SQL-99 Distinct Types 7) SQL-99 Structured Types 8) SQL-99 Functions, Methods, Procedures 9) SQL-99 Collection Types 10) SQL-99 Typed tables and views 11) SQL-99 Recursion 12) SQL/CLI or ODBC driver supports asynchronous statement execution 13) SQL/CLI or ODBC driver Supports all required SQL features 14) Transaction management functions—begin transaction, commit, abort 15) Wire protocol documentation and software My answers: 1) Yes 2) yes 3) Yes -- INFORMATION_SCHEMA 4) Yes, unless SQL99 has some wierd twist on triggers. 6), 7) Not sure what these are. 8) Functions, yes, and in PostgreSQL functions are capable of acting as procedures. 9) ??? 10) Also not sure 11) In development, expected within the next two versions. Currently we have non-SQL-standard recursion by several methods. 12) No 13) Not sure. 14) Yes 15) I think so. Feedback, please! -- -Josh Berkus Aglio Database Solutions San Francisco
Josh Berkus <josh@agliodbs.com> writes:
> Just got this "do we support it" questionnaire from a signficant commercial
> entity vaguely interested in supporting PostrgreSQL.
This looks more like an underling with a checklist than a serious
inquiry. Can you get them to specify particular capabilities that they
need? In sufficient detail that we could actually answer?
regards, tom lane
Tom,
> This looks more like an underling with a checklist than a serious
> inquiry. Can you get them to specify particular capabilities that they
> need? In sufficient detail that we could actually answer?
I'll ask, but I'm not sure that I can. The particular company is very
bureaucratic, and I doubt the person who asked me has any control over the
questionnaire.
--
-Josh Berkus
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Tom, > This looks more like an underling with a checklist than a serious > inquiry. Can you get them to specify particular capabilities that they > need? In sufficient detail that we could actually answer? Ok, talked with him. They are trying to plan OO-->DB mapping in 3 programming languages for a large project. Large enough that they would cost out implementing these SQL99 features for us if they like PostgreSQL otherwise. But they *do* need to complete the checklist for each candidate database system. So ... can anyone more familiar with SQL99 than me give some feedback? -- Josh Berkus Aglio Database Solutions San Francisco
Josh Berkus wrote:
> 6) SQL-99 Distinct Types
> 7) SQL-99 Structured Types
> 9) SQL-99 Collection Types
> 10) SQL-99 Typed tables and views
> My answers:
>
> 6), 7) Not sure what these are.
Here's the section in SQL99:
4.8 User-defined types
A user-defined type is a schema object, identified by a
<user-defined type name>. The definition of a user-defined type
specifies a number of components, including in particular a list of
attribute definitions. Although the attribute definitions are said
to define the representation of the userdefined type, in fact they
implicitly define certain functions (observers and mutators) that
are part of the interface of the user-defined type; physical
representations of user-defined type values are
implementation-dependent.
The representation of a user-defined type is expressed either as a
single data type (some predefined data type, called the source
type), in which case the user-defined type is said to be a distinct
type, or as a list of attribute definitions, in which case it is
said to be a structured type.
So if I read that correctly, they are user defined types, that are
either scalar (distinct) or composite (structured) -- so I'd say yes.
> 9) ???
From SQL99:
4.11 Collection types
A collection is a composite value comprising zero or more elements
each a value of some data type DT. If the elements of some
collection C are values of DT, then C is said to be a collection of
DT. The number of elements in C is the cardinality of C. The term
‘‘element’’ is not further defined in this part of ISO/IEC 9075.
The term ‘‘collection’’ is generic, encompassing various types (of
collection) in connection with each of which, individually, this
part of ISO/IEC 9075 defines primitive type constructors and
operators. This part of ISO/IEC 9075 supports one collection type,
arrays.
We are not yet fully compliant with SQL99 arrays, but not too far off
either, I think. We have some extensions to SQL99 behavior, that would
require breaking backward compatibility in order to do away with them.
For example, SQL99 arrays *always* start with a lower bound of 1, if I
read the spec correctly. Also multidimensional arrays in SQL99 are
"arrays of arrays", which is not quite the same as our multidimensional
arrays.
> 10) Also not sure
SQL99:
4.16.2 Referenceable tables, subtables, and supertables
A table BT whose row type is derived from a structured type ST is
called a typed table. Only a base table or a view can be a typed
table. A typed table has columns corresponding, in name and
declared type, to every attribute of ST and one other column REFC
that is the self-referencing column of BT; let REFCN be the
<column name> of REFC. The declared type of REFC is necessarily
REF(ST) and the nullability characteristic of REFC is known not
nullable. If BT is a base table, then the table constraint
‘‘UNIQUE(REFCN)’’ is implicit in the definition of BT. A typed
table is called a referenceable table. A self-referencing column
cannot be updated. Its value is determined during the insertion
of a row into the referenceable table. The value of a
system-generated selfreferencing column and a derived
self-referencing column is automatically generated when the row
is inserted into the referenceable table. The value of a
user-generated self-referencing column is supplied as part of the
candidate row to be inserted into the referenceable table.
I really don't quite understand this, but I don't think we have it ;-)
HTH,
Joe
Joe, > After re-reading it, I think it is related to (or at least similar to) > the work Tom is currently doing to allow composite types as table > attributes. That's what I thought at first as well, and told the requestor that we would support them in the next two versions. But reading that paragraph makes me think that the type is somehow supposed to contain metadata or summary data for the table itself. -- Josh Berkus Aglio Database Solutions San Francisco
Josh Berkus wrote: >>4.16.2 Referenceable tables, subtables, and supertables >> A table BT whose row type is derived from a structured type ST is >> called a typed table. Only a base table or a view can be a typed >> table. A typed table has columns corresponding, in name and >> declared type, to every attribute of ST and one other column REFC >> that is the self-referencing column of BT; let REFCN be the >> >>I really don't quite understand this, but I don't think we have it ;-) > Was the SQL99 Committee smoking crack, or what? What the heck is that > *for*? After re-reading it, I think it is related to (or at least similar to) the work Tom is currently doing to allow composite types as table attributes. Joe
Joe, Thanks for your help! > 4.16.2 Referenceable tables, subtables, and supertables > A table BT whose row type is derived from a structured type ST is > called a typed table. Only a base table or a view can be a typed > table. A typed table has columns corresponding, in name and > declared type, to every attribute of ST and one other column REFC > that is the self-referencing column of BT; let REFCN be the > > I really don't quite understand this, but I don't think we have it ;-) Ye Gods and Little Fishes!! Was the SQL99 Committee smoking crack, or what? What the heck is that *for*? -- Josh Berkus Aglio Database Solutions San Francisco
Joe Conway <mail@joeconway.com> writes:
>>> 4.16.2 Referenceable tables, subtables, and supertables
>>> A table BT whose row type is derived from a structured type ST is
>>> called a typed table. Only a base table or a view can be a typed
>>> table. A typed table has columns corresponding, in name and
>>> declared type, to every attribute of ST and one other column REFC
>>> that is the self-referencing column of BT; let REFCN be the
> After re-reading it, I think it is related to (or at least similar to)
> the work Tom is currently doing to allow composite types as table
> attributes.
The "structured type" stuff seems closely related, but I do not
understand the business about a "self-referencing column". I have a
feeling that it might be a mutant version of our notion of inheritance
...
regards, tom lane
Josh Berkus wrote: > > 4.16.2 Referenceable tables, subtables, and supertables > > A table BT whose row type is derived from a structured type > > ST is called a typed table. Only a base table or a view can be a > > typed table. A typed table has columns corresponding, in name and > > declared type, to every attribute of ST and one other column REFC > > that is the self-referencing column of BT; let REFCN be the > > > > I really don't quite understand this, but I don't think we have it > > ;-) > > Ye Gods and Little Fishes!! > > Was the SQL99 Committee smoking crack, or what? What the heck is > that *for*? Object/relational mapping?
Josh Berkus wrote: > Just got this "do we support it" questionnaire from a signficant > commercial entity vaguely interested in supporting PostrgreSQL. > Since I'm often foggy on the differences between the SQL99 and SQL92 > spec definitions of things, I thought I'd post it for feedback here: The list of supported features can be found here: http://www.postgresql.org/docs/7.4/static/features.html