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_15_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/be2502947f299a8f8f076e49eb74289558654368

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