pgsql: Doc: indexUnchanged is strictly a hint.

Doc: indexUnchanged is strictly a hint.

Clearly spell out the limitations of aminsert()'s indexUnchanged hinting
mechanism in the index AM documentation.

Oversight in commit 9dc718bd, which added the "logically unchanged
index" hint (which is used to trigger bottom-up index deletion).

Author: Peter Geoghegan <pg@bowt.ie>
Reported-By: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-By: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/CAH2-WzmU_BQ=-H9L+bxTSMQBqHMjp1DSwGypvL0gKs+dTOfkKg@mail.gmail.com
Backpatch: 14-, where indexUnchanged hinting was introduced.

Branch
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REL_14_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/df73ca35144a8711e42b82cd147ee34407553b3c

Modified Files
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doc/src/sgml/indexam.sgml | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)