Feature: numeric constants literal should be parsed as fixed-point numbers instead of floating-point numbers to avoid losing precision without notice

[youngsofun]

Summary

for numeric literal with a point, two approaches are used most commonly:

1. use floating-point as long as there is an 'e'/'E', used by MySQL, SQL server
2. use floating-point unless it is too large to fit into decimal (more than 38 digits), used by PostgreSQL、Impala、snowflake

the second way sounds more reasonable to me.

cc @andylokandy @sundy-li @BohuTANG

[BohuTANG]

Great.

These two examples will work after this issue is solved?

mysql> select 58750003716598352816469;
ERROR 1105 (HY000): Code: 1065, displayText = Unsupported literal value: 58750003716598352816469.

mysql> select 58750003716598352816469::Decimal(37,0);
ERROR 1105 (HY000): Code: 1065, displayText = Unsupported literal value: 58750003716598352816469.

[sundy-li]

Prefer 2, so we should handle the case of Literal::BigInt

[youngsofun]

Great.

These two examples will work after this issue is solved?

mysql> select 58750003716598352816469;
ERROR 1105 (HY000): Code: 1065, displayText = Unsupported literal value: 58750003716598352816469.

mysql> select 58750003716598352816469::Decimal(37,0);
ERROR 1105 (HY000): Code: 1065, displayText = Unsupported literal value: 58750003716598352816469.

yes