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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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14
src/backend/commands/operatorcmds.c
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@ -168,10 +168,22 @@ DefineOperator(List *names, List *parameters)
if (typeName2)
typeId2 = typenameTypeId(NULL, typeName2);
/*
* If only the right argument is missing, the user is likely trying to
* create a postfix operator, so give them a hint about why that does not
* work. But if both arguments are missing, do not mention postfix
* operators, as the user most likely simply neglected to mention the
* arguments.
*/
if (!OidIsValid(typeId1) && !OidIsValid(typeId2))
ereport(ERROR,
(errcode(ERRCODE_INVALID_FUNCTION_DEFINITION),
errmsg("at least one of leftarg or rightarg must be specified")));
errmsg("operator argument types must be specified")));
if (!OidIsValid(typeId2))
ereport(ERROR,
(errcode(ERRCODE_INVALID_FUNCTION_DEFINITION),
errmsg("operator right argument type must be specified"),
errdetail("Postfix operators are not supported.")));
if (typeName1)
{