Support for SET statements.

[lmwnshn]

SET talks directly to the settings manager, poking the values.

With parser SET support yoinked from @thepinetree, thanks!

Known issues

• SettingsManager assumes that 1 setting = 1 constant value expression. This is not necessarily the case in postgres, which can have SET foo TO bar,baz.
• Legacy? ActionContext and SettingsCallback stuff is not being used by DBMain or throughout the system.

Example usage

Support for invalid values (type mismatch):

terrier=# set record_buffer_segment_size to a;
ERROR:  invalid value for parameter "record_buffer_segment_size": "a"
terrier=# \errverbose
ERROR:  22023: invalid value for parameter "record_buffer_segment_size": "a"
LOCATION:  /home/cmudb/CLionProjects/terrier/src/settings/settings_manager.cpp:272

Support for invalid values (out of range):

terrier=# set record_buffer_segment_size to -1;
ERROR:  -1 is outside the valid range for parameter "record_buffer_segment_size" (1 .. 1000000)
terrier=# \errverbose
ERROR:  22023: -1 is outside the valid range for parameter "record_buffer_segment_size" (1 .. 1000000)
LOCATION:  /home/cmudb/CLionProjects/terrier/src/settings/settings_manager.cpp:140

Support for valid value but runtime error:

terrier=# set record_buffer_segment_size to 1;
ERROR:  Callback failed after setting "record_buffer_segment_size" from "100000" to "1", revert succeeded.
terrier=# \errverbose
ERROR:  XX000: Callback failed after setting "record_buffer_segment_size" from "100000" to "1", revert succeeded.
LOCATION:  /home/cmudb/CLionProjects/terrier/src/settings/settings_manager.cpp:140

Support for valid value being set (I don't know how to show a setting, you can see it changed in the error message):

terrier=# set record_buffer_segment_size to 100001;
SET
terrier=# set record_buffer_segment_size to 1;
ERROR:  Callback failed after setting "record_buffer_segment_size" from "100001" to "1", revert succeeded.

terrier=# set record_buffer_segment_size to 5;
SET
terrier=# set record_buffer_segment_size to 1;
ERROR:  Callback failed after setting "record_buffer_segment_size" from "5" to "1", revert succeeded.

---

Also added support for DEFAULT. There was a bug with the settings manager that wouldn't let you define more than one string setting, that was fixed.

[thepinetree]

Did a pass. Looks good too me.

[mbutrovich]

Investigating JUnit failures...

Traffic Cop is broken.

[codecov]

Codecov Report

Merging #1073 into master will decrease coverage by 0.24%.
The diff coverage is 58.49%.

@@            Coverage Diff             @@
##           master    #1073      +/-   ##
==========================================
- Coverage   81.47%   81.22%   -0.25%     
==========================================
  Files         650      649       -1     
  Lines       42978    42281     -697     
==========================================
- Hits        35015    34343     -672     
+ Misses       7963     7938      -25     

Impacted Files	Coverage Δ
...lude/parser/expression/constant_value_expression.h	96.29% <ø> (ø)
src/include/traffic_cop/traffic_cop.h	100.00% <ø> (ø)
...rc/parser/expression/constant_value_expression.cpp	86.48% <0.00%> (-8.15%)	⬇️
src/parser/postgresparser.cpp	84.96% <42.85%> (-0.54%)	⬇️
src/traffic_cop/traffic_cop.cpp	72.24% <46.66%> (-8.72%)	⬇️
src/network/postgres/postgres_network_commands.cpp	72.66% <60.00%> (-7.57%)	⬇️
src/settings/settings_manager.cpp	76.10% <64.70%> (+6.24%)	⬆️
src/include/main/db_main.h	94.04% <100.00%> (+0.41%)	⬆️
src/include/network/network_util.h	100.00% <100.00%> (ø)
src/include/parser/variable_set_statement.h	93.75% <100.00%> (+4.27%)	⬆️
... and 18 more

---

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[mbutrovich]

LGTM