Enable Shared-Cache Mode for opened database

[haaawk]

According to documentation this mode can increase database performance: https://www.sqlite.org/sharedcache.html

My tests showed improvement both when using 1 client and 100 clients.

For sigle client the throughput increased by 14%.
For 100 clients the throughput increased by 27%.
On the same time latencies have been lowered.

The results for sqld running locally:

1 client with no sharedcache:
Summary:
Total: 60.0012 secs
Slowest: 0.0221 secs
Fastest: 0.0009 secs
Average: 0.0011 secs
Requests/sec: 895.4821

Latency distribution:
    10% in 0.0009 secs
    25% in 0.0010 secs
    50% in 0.0011 secs
    75% in 0.0012 secs
    90% in 0.0013 secs
    95% in 0.0014 secs
    99% in 0.0018 secs

1 client with sharedcache:
Summary:
Total: 60.0008 secs
Slowest: 0.0187 secs
Fastest: 0.0008 secs
Average: 0.0010 secs
Requests/sec: 1042.3534
Latency distribution:
10% in 0.0008 secs
25% in 0.0009 secs
50% in 0.0009 secs
75% in 0.0010 secs
90% in 0.0011 secs
95% in 0.0012 secs
99% in 0.0016 secs

100 clients with no sharedcache:
Summary:
Total: 60.0359 secs
Slowest: 0.0962 secs
Fastest: 0.0103 secs
Average: 0.0368 secs
Requests/sec: 2716.9230
Latency distribution:
10% in 0.0311 secs
25% in 0.0338 secs
50% in 0.0368 secs
75% in 0.0396 secs
90% in 0.0422 secs
95% in 0.0439 secs
99% in 0.0480 secs

100 clients with sharedcache:
Summary:
Total: 60.0218 secs
Slowest: 0.0828 secs
Fastest: 0.0075 secs
Average: 0.0267 secs
Requests/sec: 3744.2703
Latency distribution:
10% in 0.0225 secs
25% in 0.0242 secs
50% in 0.0262 secs
75% in 0.0287 secs
90% in 0.0314 secs
95% in 0.0332 secs
99% in 0.0377 secs

[haaawk]

Single client results with no sharedcache:

╰──> hey -c 1 -z 1m -m POST -d '{ "statements": [{"q" : "SELECT * FROM t"}] }' http://127.0.0.1:8080/

Summary:
  Total:        60.0012 secs
  Slowest:      0.0221 secs
  Fastest:      0.0009 secs
  Average:      0.0011 secs
  Requests/sec: 895.4821
 

Response time histogram:
  0.001 [1]     |
  0.003 [53670] |■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■
  0.005 [32]    |
  0.007 [9]     |
  0.009 [4]     |
  0.011 [4]     |
  0.014 [6]     |
  0.016 [1]     |
  0.018 [1]     |
  0.020 [0]     |
  0.022 [2]     |


Latency distribution:
  10% in 0.0009 secs
  25% in 0.0010 secs
  50% in 0.0011 secs
  75% in 0.0012 secs
  90% in 0.0013 secs
  95% in 0.0014 secs
  99% in 0.0018 secs

Details (average, fastest, slowest):
  DNS+dialup:   0.0000 secs, 0.0009 secs, 0.0221 secs
  DNS-lookup:   0.0000 secs, 0.0000 secs, 0.0000 secs
  req write:    0.0000 secs, 0.0000 secs, 0.0003 secs
  resp wait:    0.0011 secs, 0.0008 secs, 0.0220 secs
  resp read:    0.0000 secs, 0.0000 secs, 0.0007 secs

Status code distribution:
  [200] 53730 responses

Single client results with sharedcache:

╰──> hey -c 1 -z 1m -m POST -d '{ "statements": [{"q" : "SELECT * FROM t"}] }' http://127.0.0.1:8080/

Summary:
  Total:        60.0008 secs
  Slowest:      0.0187 secs
  Fastest:      0.0008 secs
  Average:      0.0010 secs
  Requests/sec: 1042.3534
 

Response time histogram:
  0.001 [1]     |
  0.003 [62525] |■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■
  0.004 [13]    |
  0.006 [1]     |
  0.008 [0]     |
  0.010 [0]     |
  0.012 [0]     |
  0.013 [1]     |
  0.015 [0]     |
  0.017 [0]     |
  0.019 [1]     |


Latency distribution:
  10% in 0.0008 secs
  25% in 0.0009 secs
  50% in 0.0009 secs
  75% in 0.0010 secs
  90% in 0.0011 secs
  95% in 0.0012 secs
  99% in 0.0016 secs

Details (average, fastest, slowest):
  DNS+dialup:   0.0000 secs, 0.0008 secs, 0.0187 secs
  DNS-lookup:   0.0000 secs, 0.0000 secs, 0.0000 secs
  req write:    0.0000 secs, 0.0000 secs, 0.0004 secs
  resp wait:    0.0009 secs, 0.0007 secs, 0.0185 secs
  resp read:    0.0000 secs, 0.0000 secs, 0.0006 secs

Status code distribution:
  [200] 62542 responses

100 clients with no sharedcache:

╰──> hey -c 100 -z 1m -m POST -d '{ "statements": [{"q" : "SELECT * FROM t"}] }' http://127.0.0.1:8080/

Summary:
  Total:        60.0359 secs
  Slowest:      0.0962 secs
  Fastest:      0.0103 secs
  Average:      0.0368 secs
  Requests/sec: 2716.9230
 

Response time histogram:
  0.010 [1]     |
  0.019 [14]    |
  0.027 [2523]  |■
  0.036 [68122] |■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■
  0.045 [86519] |■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■
  0.053 [5463]  |■■■
  0.062 [335]   |
  0.070 [121]   |
  0.079 [9]     |
  0.088 [4]     |
  0.096 [2]     |


Latency distribution:
  10% in 0.0311 secs
  25% in 0.0338 secs
  50% in 0.0368 secs
  75% in 0.0396 secs
  90% in 0.0422 secs
  95% in 0.0439 secs
  99% in 0.0480 secs

Details (average, fastest, slowest):
  DNS+dialup:   0.0000 secs, 0.0103 secs, 0.0962 secs
  DNS-lookup:   0.0000 secs, 0.0000 secs, 0.0000 secs
  req write:    0.0000 secs, 0.0000 secs, 0.0015 secs
  resp wait:    0.0367 secs, 0.0074 secs, 0.0961 secs
  resp read:    0.0001 secs, 0.0000 secs, 0.0012 secs

Status code distribution:
  [200] 163113 responses

100 clients with sharedcache:

╰──> hey -c 100 -z 1m -m POST -d '{ "statements": [{"q" : "SELECT * FROM t"}] }' http://127.0.0.1:8080/

Summary:
  Total:        60.0218 secs
  Slowest:      0.0828 secs
  Fastest:      0.0075 secs
  Average:      0.0267 secs
  Requests/sec: 3744.2703
 

Response time histogram:
  0.008 [1]     |
  0.015 [11]    |
  0.023 [24283] |■■■■■■
  0.030 [164856]        |■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■
  0.038 [33285] |■■■■■■■■
  0.045 [1787]  |
  0.053 [333]   |
  0.060 [111]   |
  0.068 [55]    |
  0.075 [11]    |
  0.083 [5]     |


Latency distribution:
  10% in 0.0225 secs
  25% in 0.0242 secs
  50% in 0.0262 secs
  75% in 0.0287 secs
  90% in 0.0314 secs
  95% in 0.0332 secs
  99% in 0.0377 secs

Details (average, fastest, slowest):
  DNS+dialup:   0.0000 secs, 0.0075 secs, 0.0828 secs
  DNS-lookup:   0.0000 secs, 0.0000 secs, 0.0000 secs
  req write:    0.0000 secs, 0.0000 secs, 0.0048 secs
  resp wait:    0.0266 secs, 0.0058 secs, 0.0827 secs
  resp read:    0.0001 secs, 0.0000 secs, 0.0056 secs

Status code distribution:
  [200] 224738 responses

[haaawk]

I'm about to run benchmarks for writes as well