String x might contain trimming spaces. And it needs to be trimmed. For
example, in csv files, there might be trimming spaces in a field that
ought to meet a query condition that contains the value without
trimming spaces. This applies to both intCast and floatCast functions.
Queue output items and reuse them.
Remove the unneeded type system in sql and just use the Go type system.
In best case this is more than an order of magnitude speedup:
```
BenchmarkSelectAll_1M-12 1 1841049400 ns/op 274299728 B/op 4198522 allocs/op
BenchmarkSelectAll_1M-12 14 84833400 ns/op 169228346 B/op 3146541 allocs/op
```
This change adds support for casting strings to Timestamp via CAST:
`CAST('2010T' AS TIMESTAMP)`
It also implements the following date-time functions:
- UTCNOW()
- DATE_ADD()
- DATE_DIFF()
- EXTRACT()
For values passed to these functions, date-types are automatically
inferred.
- New parser written from scratch, allows easier and complete parsing
of the full S3 Select SQL syntax. Parser definition is directly
provided by the AST defined for the SQL grammar.
- Bring support to parse and interpret SQL involving JSON path
expressions; evaluation of JSON path expressions will be
subsequently added.
- Bring automatic type inference and conversion for untyped
values (e.g. CSV data).
