1. CTEs
Past, Present, and Future
PGDay NYC 2013/03/22
Copyright© 2013
David Fetter
david@fetter.org

3. Past (pre-8.4)
ø

4. ☹
Past (pre-8.4)

5. Past (8.4)
- Add support for WITH clauses (CTEs),
including WITH RECURSIVE
(Yoshiyuki Asaba, Tatsuo Ishii, Tom)

6. Past CTEs
WITH [RECURSIVE] t1 [(column type,…)] AS
(
[SELECT | VALUES]
[UNION [ALL]
[SELECT]
),
t2 AS…tn AS…
SELECT…

7. SQL is Turing-Complete

9. Travelling Salesman Problem
Given a number of cities and the costs of travelling
from any city to any other city, what is the least-
cost round-trip route that visits each city exactly
once and then returns to the starting city?

10. Present (9.1)
Allow data-modification commands
(INSERT/UPDATE/DELETE) in
WITH clauses

11. YAY!
WITH [RECURSIVE] t1 [(column type,…)] AS
(
[SELECT | VALUES |
(INSERT | UPDATE | DELETE) [RETURNING]]
[UNION [ALL]
[SELECT | VALUES |
(INSERT | UPDATE | DELETE) [RETURNING]]
), ...
(SELECT | INSERT | UPDATE | DELETE) …

12. Future (9.4+)
Let's think this through.

13. NOW!
WITH [RECURSIVE] t1 [(column type,…)] AS
(
[SELECT | VALUES |
(INSERT | UPDATE | DELETE) [RETURNING]]
[UNION [ALL]
[SELECT | VALUES |
(INSERT | UPDATE | DELETE) [RETURNING]]
), ...
(SELECT | INSERT | UPDATE | DELETE) …

14. Data Manipulation
WITH [RECURSIVE] t1 [(column type,…)]
AS (
DML
[UNION [ALL]
DML]
), ...
DML

15. Actually...

16. Data Manipulation
WITH [RECURSIVE] t1 [(column type,…)]
AS (
DML
[(UNION|INTERSECT) [ALL]
DML]
), ...
DML

17. DML That Can't
Return Rows...YET!
Return Rows...YET!
• COPY
• DO
• EXPLAIN
• SHOW

18. Fortunately...
commit 7a3e30e608a25800a1f7fdfaaca4da3f0ac0fb07Author: Tom Lane <tgl@sss.pgh.pa.us>Date:
Sat Aug 12 02:52:06 2006 +0000 Add INSERT/UPDATE/DELETE RETURNING, with basic docs
and regression tests. plpgsql support to come later. Along the way, convert execMain's SELECT
INTO support into a DestReceiver, in order to eliminate some ugly special cases. Jonah Harris
and Tom Lane doc/src/sgml/ref/delete.sgml | 56 +++++++++- doc/src/sgml/ref/insert.sgml | 65 ++++++++++-- doc/src/sgml/ref/update.sgml | 57 +++
++++++- src/backend/access/common/printtup.c | 8 +- src/backend/commands/prepare.c | 9 +- src/backend/executor/execMain.c | 655 ++++++++++++++++++++++++
++++++++++++++++++++++++++++++++++++++++++++++++++++++----------------------------------- src/backend/executor/spi.c | 9 +- src/backend/nodes/copyfuncs.c |
9 +- src/backend/nodes/equalfuncs.c | 9 +- src/backend/nodes/outfuncs.c | 4 +- src/backend/nodes/readfuncs.c | 4 +- src/backend/optimizer/plan/planagg.c | 3
+- src/backend/optimizer/plan/planner.c | 39 ++++++- src/backend/optimizer/plan/setrefs.c | 137 ++++++++++++++++++------ src/backend/optimizer/prep/prepjointree.c | 6 +-
src/backend/optimizer/prep/preptlist.c | 39 ++++++- src/backend/optimizer/util/clauses.c | 5 +- src/backend/parser/analyze.c | 89 ++++++++++++++--
src/backend/parser/gram.y | 20 +++- src/backend/parser/keywords.c | 3 +- src/backend/tcop/dest.c | 9 +- src/backend/tcop/pquery.c | 152 +++++
++++++++++----------- src/backend/tcop/utility.c | 4 +- src/backend/utils/adt/ruleutils.c | 123 +++++++++++++++------- src/include/catalog/catversion.h | 4 +-
src/include/executor/executor.h | 3 +- src/include/nodes/execnodes.h | 4 +- src/include/nodes/parsenodes.h | 24 ++++- src/include/optimizer/planmain.h | 5 +-
src/include/tcop/dest.h | 9 +- src/include/utils/portal.h | 16 ++- src/test/regress/expected/returning.out | 195 ++++++++++++++++++++++++++++++++++
src/test/regress/parallel_schedule | 4 +- src/test/regress/serial_schedule | 3 +- src/test/regress/sql/returning.sql | 87 +++++++++++++++ 35 files changed, 1459
insertions(+), 409 deletions(-)
doc/src/sgml/ref/delete.sgml | 56 +++++++++- doc/src/sgml/ref/insert.sgml | 65 ++++++++++-- doc/src/sgml/ref/update.sgml | 57 +++++++++-
src/backend/access/common/printtup.c | 8 +- src/backend/commands/prepare.c | 9 +- src/backend/executor/execMain.c | 655 +++++++++++++++++++++++++++++++
+++++++++++++++++++++++++++++++++++++++++++++++----------------------------------- src/backend/executor/spi.c | 9 +- src/backend/nodes/copyfuncs.c | 9 +-
src/backend/nodes/equalfuncs.c | 9 +- src/backend/nodes/outfuncs.c | 4 +- src/backend/nodes/readfuncs.c | 4 +- src/backend/optimizer/plan/planagg.c | 3 +-
src/backend/optimizer/plan/planner.c | 39 ++++++- src/backend/optimizer/plan/setrefs.c | 137 ++++++++++++++++++------ src/backend/optimizer/prep/prepjointree.c | 6 +-
src/backend/optimizer/prep/preptlist.c | 39 ++++++- src/backend/optimizer/util/clauses.c | 5 +- src/backend/parser/analyze.c | 89 ++++++++++++++--
src/backend/parser/gram.y | 20 +++- src/backend/parser/keywords.c | 3 +- src/backend/tcop/dest.c | 9 +- src/backend/tcop/pquery.c | 152 +++++
++++++++++----------- src/backend/tcop/utility.c | 4 +- src/backend/utils/adt/ruleutils.c | 123 +++++++++++++++------- src/include/catalog/catversion.h | 4 +-
src/include/executor/executor.h | 3 +- src/include/nodes/execnodes.h | 4 +- src/include/nodes/parsenodes.h | 24 ++++- src/include/optimizer/planmain.h | 5 +-
src/include/tcop/dest.h | 9 +- src/include/utils/portal.h | 16 ++- src/test/regress/expected/returning.out | 195 ++++++++++++++++++++++++++++++++++
src/test/regress/parallel_schedule | 4 +- src/test/regress/serial_schedule | 3 +- src/test/regress/sql/returning.sql | 87 +++++++++++++++ 35 files changed, 1459
insertions(+), 409 deletions(-)

19. Why not go the whole route?

20. Data
{{Manipula,Defini}tion,Control}
{{Manipula,Defini}tion,Control}
WITH [RECURSIVE] t1 [(column type,…)]
AS (
D(M|C|D)L
[(UNION|INTERSECT) [ALL]
D(M|C|D)L]
), ...
D(M|C|D)L

21. OMG!

22. What Needs to Happen?

23. Powers Needed
1.Return rows (RETURNING)
2.Use rowsets (FROM | USING)
(later)
3.Wrap in CTE machinery

24. Bikesheds
• Which ones first?
• UPDATE RETURNING (NEW & OLD)
• What should RETURNING be able to return?
• What does FROM/USING even mean?
• et cetæra

25. Let's Make This Be!

26. Questions?
Comments!
Comments!

27. Thanks!
Copyright© 2013
David Fetter
david@fetter.org