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Drop the rule against included index columns duplicating key columns.

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The initial version of the included-index-column feature stated that
included columns couldn't be the same as any key column of the index.
While it'd be pretty silly to do that, since the included column would be
entirely redundant, we've never prohibited redundant index columns before
so it's not very consistent to do so here.  Moreover, the prohibition
was itself badly implemented, so that it failed to reject columns that
were effectively identical but not spelled quite alike, as reported by
Aditya Toshniwal.

(Moreover, it's not hard to imagine that for some non-btree index types,
such cases would be non-silly anyhow: the index might use a lossy
representation for key columns but be able to support retrieval of the
original form of included columns.)

Hence, let's just drop the prohibition.

In passing, do some copy-editing on the documentation for the
included-column feature.

Yugo Nagata; documentation and test corrections by me

Discussion: https://postgr.es/m/CAM9w-_mhBCys4fQNfaiQKTRrVWtoFrZ-wXmDuE9Nj5y-Y7aDKQ@mail.gmail.com
This commit is contained in:
Tom Lane
2018-07-18 14:43:03 -04:00
parent 65976cd86a
commit eb00eb4e8c
8 changed files with 58 additions and 64 deletions
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7
src/backend/commands/indexcmds.c
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@ -369,11 +369,6 @@ DefineIndex(Oid relationId,
Snapshot snapshot;
int i;
if (list_intersection(stmt->indexParams, stmt->indexIncludingParams) != NIL)
ereport(ERROR,
(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
errmsg("included columns must not intersect with key columns")));
/*
* count key attributes in index
*/
@ -596,7 +591,7 @@ DefineIndex(Oid relationId,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("access method \"%s\" does not support unique indexes",
accessMethodName)));
if (list_length(stmt->indexIncludingParams) > 0 && !amRoutine->amcaninclude)
if (stmt->indexIncludingParams != NIL && !amRoutine->amcaninclude)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("access method \"%s\" does not support included columns",