Re: Import: empty string and expression

> > String:
> > How to distinguish NULL and empty?
> >
> > In the COPY command, it conside no quoted empty as NULL and quoted ones as empty.
> > This rule not defined in the CSV standard(RFC4180).
> > For example:
> > A,,B has three item: 'A', NULL and 'B'
> > A,"",B has three item: 'A', empty and 'B'
> > Should we follow this rule?
> > I think it is good.
>
> Sounds good to me.

With the width-delimiter, user can set empty values by "5,,12" or "5,0,12".
Should we add NULL-value support? Like: "5,<NULL>,12"

How about other types? boolean, integer, float, and so on.
This is my idea:
For String, the user can select one chioce:
"empty" (generate "FORCE NOT NULL" option for COPY or '' for INSERT),
"NULL" (left nochange, for column nullable column)
"ERROR" (don't generate statement, log only).
"CONSTANT" (user-defined string)
All of them act on NULL.
For others:
"NULL" (left nochange)
"ERROR" (don't generate statement, log only).
"CONSTANT" (user-defined string) or
[other options depend on type]
All of them act on NULL or empty.

Until now, I have no idea with array type.

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Quan Zongliang
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