DB-side UPSERT optimiziation support

[peterbroadhurst]

• Provides a new feature option for DB providers to build a DB-optimized UPSERT functionality
  • Implementation for PSQL provided for re-use by repos using this module
  • Slightly annoying workaround to sq semantics called out in comments
• Provides a new optimization type that requests DB optimization of the upsert
  • Didn't feel ready to make this the default
  • Falls back to update optimization if not available on DB provider

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.96%. Comparing base (b6bcbb4) to head (e1a20e0).
Report is 6 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #138   +/-   ##
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  Coverage   99.96%   99.96%           
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  Files          79       80    +1     
  Lines        6507     6567   +60     
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+ Hits         6505     6565   +60     
  Misses          1        1           
  Partials        1        1           

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[awrichar]

I believe this alternate cheat would also work (using a single space as the table name, and then not performing any stripping):

insert = sq.Insert(table).Columns(insertCols...).Values(insertValues...)
update := sq.Update(" " /* cheat to avoid table name */)
for _, c := range updateCols {
	update = update.Set(c, values[c])
}
updateSQL, updateValues, err := update.ToSql()
if err != nil {
	return insert, i18n.NewError(ctx, i18n.MsgDBErrorBuildingStatement, err)
}
return insert.Suffix(fmt.Sprintf("ON CONFLICT (%s) DO", idColumn)).
	SuffixExpr(sq.Expr(updateSQL, updateValues...)).
	Suffix("RETURNING " + returnCol), nil

Happy for you to keep it as is or switch it (not sure either is better/worse - just noting it as a possibility).

[peterbroadhurst]

Going to merge for now, thank you though 👍