DbColumn

DbColumn is an object describing a column of a relation (a regular data table or some similar object like SQL view etc.) in a database.

Properties

Name	Type	Description
name	String	Name (identifier) of this column
comment	String	Comment for this column
type	String	Name of the data type
size	int	Maximum size of the data (length for VARCHAR, precision for DECIMAL etc.). The exact meaning (units etc.) and the mere existence meaning depends of the type.
scale	int	For DECIMAL, his synonyms and/or derived types, (NUMERIC etc.) means the length of the fractional part. Must be absent for other types.
default	String	The DEFAULT clause of the corresponding CREATE/ALTER TABLE statement. Always presented as a String, including numeric types. Explicit DEFAULT NULL is defined by a 4-letter string 'NULL'.
nullable	Boolean	false for NOT NULL columns, true otherwise.
min	String	The minimal allowed value. Corresponds to the HTML INPUT's min attribute. May be used in autogenerated validation procedures, forwarded to UI components etc.
max	String	The maximal allowed value. Corresponds to the HTML INPUT's max attribute. May be used in autogenerated validation procedures, forwarded to UI components etc.
pattern	String	The regular expression to test values against. Corresponds to the HTML INPUT's pattern attribute. May be used in autogenerated validation procedures, forwarded to UI components etc.

Domain-specific language

The class implements a tiny DSL to build DbColumn objects from formatted strings.

column    ::= ( physical | reference ) nullable? ("=" default)? range? re? ("//" comment )?

physical  ::= type dimension?
dimension ::= "(" size ("," scale)? ")"

nullable  ::= "?" | "!"

range     ::= "{" min? ".." max? "}"
re        ::= "/" pattern "/"

Where:

• for reference, see DbReference;
• when the range is specified, min or max may be omitted, but not both
• default, min and max literals are not delimited, so they must not contain any special characters used by delimiters by the DSL itself (e. g. max can't contain '}', but no ordinal type allow such constants, so it's not really a restriction). Round braces (and so, function calls, compound expressions etc.) are allowed in default.
• the nullable availability and meaning depends on default:

nullable	deault	example	The column is...
		int	NULLABLE
	defined	int = 0	NOT NULL
!		int!	NOT NULL
?	defined	int ?= 0	NULLABLE
?		int?	n/a
!	defined	int!=0	n/a

Constructor

Can accept the 1st parameter in two forms:

• an Object to copy to this
• or a String to parse

const ref = new DbColumn ({type: 'int', comment: 'ID', default: '0', nullable: false})
// or
const ref = new DbColumn ('int=0')

Methods

parse ()

Parses this.src (where the constructor puts the 1st string argument) into local properties. Used by the constructor.

parseDefault ()

Slices the this.type part after = into this.default. Used by the constructor.

parsePattern ()

Slices the this.default or this.type part between the last two /s into this.default. Used by the constructor.

parseRange ()

Slices the this.default or this.type part between { and } into this.default. Used by the constructor.

parseNullable ()

Set the nullable property based on this.default and the last character of this.type. Used by the constructor.

parseDimension ()

Parses this.type into this.type per se, this.size and this.scale. Used by the constructor.