[kvexec] customized operator for count aggregation

[max-hoffman]

Operators that count the number of rows in a relation don't have to deserialize those KV's from storage (ex: select count(y) from xy where x > 1). There are some circumstances where we have to check for field nullability, but otherwise we can just count the KV's returned by the source iterator.

[max-hoffman]

#benchmark

[github-actions]

@max-hoffman workflow run: https://github.com/dolthub/dolt/actions/runs/10288877165

[coffeegoddd]

@max-hoffman DOLT

comparing_percentages
100.000000 to 100.000000

version	result	total
17c017f	ok	5937457

version	total_tests
17c017f	5937457

correctness_percentage
100.0

[coffeegoddd]

@max-hoffman DOLT

test_name	from_latency_p95	to_latency_p95	is_faster
tpcc-scale-factor-1	59.99	62.19	0

test_name	server_name	server_version	tps	test_name	server_name	server_version	tps	is_faster
tpcc-scale-factor-1	dolt	b2f0662	39.37	tpcc-scale-factor-1	dolt	17c017f	39.75	0

[coffeegoddd]

@coffeegoddd DOLT

comparing_percentages
100.000000 to 100.000000

version	result	total
f8fc91f	ok	5937457

version	total_tests
f8fc91f	5937457

correctness_percentage
100.0

[coffeegoddd]

@max-hoffman DOLT

read_tests	from_latency_median	to_latency_median	is_faster
covering_index_scan	2.97	1.18	1
groupby_scan	17.32	17.01	0
index_join	2.66	2.66	0
index_join_scan	2.14	2.14	0
index_scan	54.83	54.83	0
oltp_point_select	0.3	0.29	0
oltp_read_only	5.88	5.88	0
select_random_points	0.65	0.65	0
select_random_ranges	0.83	0.8	0
table_scan	54.83	54.83	0
types_table_scan	142.39	144.97	0

write_tests	from_latency_median	to_latency_median	is_faster
oltp_delete_insert	5.88	5.88	0
oltp_insert	2.97	2.97	0
oltp_read_write	12.08	11.87	0
oltp_update_index	3.02	2.97	0
oltp_update_non_index	2.97	2.91	0
oltp_write_only	6.09	6.09	0
types_delete_insert	6.43	6.43	0

[max-hoffman]

#benchmark

[github-actions]

@max-hoffman workflow run: https://github.com/dolthub/dolt/actions/runs/10295020839

[coffeegoddd]

@max-hoffman DOLT

test_name	from_latency_p95	to_latency_p95	is_faster
tpcc-scale-factor-1	61.08	61.08	0

test_name	server_name	server_version	tps	test_name	server_name	server_version	tps	is_faster
tpcc-scale-factor-1	dolt	a50b1b7	39.0	tpcc-scale-factor-1	dolt	bb31dbd	39.84	0

[coffeegoddd]

@max-hoffman DOLT

read_tests	from_latency_median	to_latency_median	is_faster
covering_index_scan	2.91	1.21	1
groupby_scan	17.01	17.01	0
index_join	2.66	2.61	0
index_join_scan	2.14	2.18	0
index_scan	54.83	54.83	0
oltp_point_select	0.3	0.3	0
oltp_read_only	5.99	5.99	0
select_random_points	0.65	0.65	0
select_random_ranges	0.83	0.8	0
table_scan	55.82	54.83	0
types_table_scan	142.39	142.39	0

write_tests	from_latency_median	to_latency_median	is_faster
oltp_delete_insert	5.99	5.99	0
oltp_insert	3.02	2.97	0
oltp_read_write	12.08	12.08	0
oltp_update_index	3.02	3.02	0
oltp_update_non_index	2.97	2.97	0
oltp_write_only	6.21	6.21	0
types_delete_insert	6.55	6.43	0

[zachmu]

LGTM

[zachmu]

spacing

[coffeegoddd]

@max-hoffman DOLT

comparing_percentages
100.000000 to 100.000000

version	result	total
ff89161	ok	5937457

version	total_tests
ff89161	5937457

correctness_percentage
100.0

[coffeegoddd]

@max-hoffman DOLT

comparing_percentages
100.000000 to 100.000000

version	result	total
4fc3498	ok	5937457

version	total_tests
4fc3498	5937457

correctness_percentage
100.0

[coffeegoddd]

@max-hoffman DOLT

comparing_percentages
100.000000 to 100.000000

version	result	total
d35a051	ok	5937457

version	total_tests
d35a051	5937457

correctness_percentage
100.0

[coffeegoddd]

@coffeegoddd DOLT

comparing_percentages
100.000000 to 100.000000

version	result	total
20c6e26	ok	5937457

version	total_tests
20c6e26	5937457

correctness_percentage
100.0