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Remove support for postfix (right-unary) operators.

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This feature has been a thorn in our sides for a long time, causing
many grammatical ambiguity problems.  It doesn't seem worth the
pain to continue to support it, so remove it.

There are some follow-on improvements we can make in the grammar,
but this commit only removes the bare minimum number of productions,
plus assorted backend support code.

Note that pg_dump and psql continue to have full support, since
they may be used against older servers.  However, pg_dump warns
about postfix operators.  There is also a check in pg_upgrade.

Documentation-wise, I (tgl) largely removed the "left unary"
terminology in favor of saying "prefix operator", which is
a more standard and IMO less confusing term.

I included a catversion bump, although no initial catalog data
changes here, to mark the boundary at which oprkind = 'r'
stopped being valid in pg_operator.

Mark Dilger, based on work by myself and Robert Haas;
review by John Naylor

Discussion: https://postgr.es/m/38ca86db-42ab-9b48-2902-337a0d6b8311@2ndquadrant.com
This commit is contained in:
Tom Lane
2020-09-17 19:38:05 -04:00
parent 76f412ab31
commit 1ed6b89563
32 changed files with 279 additions and 339 deletions
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24
src/tutorial/syscat.source
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@ -96,36 +96,22 @@ SELECT n.nspname, r.rolname, format_type(t.oid, null) as typname
--
-- lists all left unary operators
-- lists all prefix operators
--
SELECT n.nspname, o.oprname AS left_unary,
SELECT n.nspname, o.oprname AS prefix_op,
format_type(right_type.oid, null) AS operand,
format_type(result.oid, null) AS return_type
FROM pg_namespace n, pg_operator o,
pg_type right_type, pg_type result
WHERE o.oprnamespace = n.oid
and o.oprkind = 'l' -- left unary
and o.oprkind = 'l' -- prefix ("left unary")
and o.oprright = right_type.oid
and o.oprresult = result.oid
ORDER BY nspname, operand;
--
-- lists all right unary operators
--
SELECT n.nspname, o.oprname AS right_unary,
format_type(left_type.oid, null) AS operand,
format_type(result.oid, null) AS return_type
FROM pg_namespace n, pg_operator o,
pg_type left_type, pg_type result
WHERE o.oprnamespace = n.oid
and o.oprkind = 'r' -- right unary
and o.oprleft = left_type.oid
and o.oprresult = result.oid
ORDER BY nspname, operand;
--
-- lists all binary operators
-- lists all infix operators
--
SELECT n.nspname, o.oprname AS binary_op,
format_type(left_type.oid, null) AS left_opr,
@ -134,7 +120,7 @@ SELECT n.nspname, o.oprname AS binary_op,
FROM pg_namespace n, pg_operator o, pg_type left_type,
pg_type right_type, pg_type result
WHERE o.oprnamespace = n.oid
and o.oprkind = 'b' -- binary
and o.oprkind = 'b' -- infix ("binary")
and o.oprleft = left_type.oid
and o.oprright = right_type.oid
and o.oprresult = result.oid