pgsql: Generalize relation analyze in table AM interface

Generalize relation analyze in table AM interface

Currently, there is just one algorithm for sampling tuples from a table written
in acquire_sample_rows(). Custom table AM can just redefine the way to get the
next block/tuple by implementing scan_analyze_next_block() and
scan_analyze_next_tuple() API functions.

This approach doesn't seem general enough. For instance, it's unclear how to
sample this way index-organized tables. This commit allows table AM to
encapsulate the whole sampling algorithm (currently implemented in
acquire_sample_rows()) into the relation_analyze() API function.

Discussion: https://postgr.es/m/CAPpHfdurb9ycV8udYqM%3Do0sPS66PJ4RCBM1g-bBpvzUfogY0EA%40mail.gmail.com
Reviewed-by: Pavel Borisov, Matthias van de Meent

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/27bc1772fc814946918a5ac8ccb9b5c5ad0380aa

Modified Files
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src/backend/access/heap/heapam_handler.c | 29 ++++++---
src/backend/access/table/tableamapi.c | 2 -
src/backend/commands/analyze.c | 54 ++++++++--------
src/include/access/heapam.h | 9 +++
src/include/access/tableam.h | 106 +++++++------------------------
src/include/commands/vacuum.h | 19 ++++++
src/include/foreign/fdwapi.h | 6 +-
7 files changed, 100 insertions(+), 125 deletions(-)