pgsql: Improve histogram-filling loop in new compute_array_stats() code

Improve histogram-filling loop in new compute_array_stats() code.

Do "frac" arithmetic in int64 to prevent overflow with large statistics
targets, and improve the comments so people have some chance of
understanding how it works.

Alexander Korotkov and Tom Lane

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/4fb694aebc524f2085152d8c98a85e01ef6136f4

Modified Files
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src/backend/utils/adt/array_typanalyze.c |   63 +++++++++++++++++++++---------
1 files changed, 44 insertions(+), 19 deletions(-)