dsave

Saves global tables to disk as splayed, enumerated, indexed kdb+ tables.

Syntax: x dsave y, dsave[x;y]

Where

  • x is the save path as a symbol or symbol list
  • y is a list of table names

returns the list of table names, having saved the table/s as a side effect. (Since V3.2 2014.05.07.)

The first column of each table saved has the `p attribute applied to it. If the path is a list, the first item is the HDB root (where the sym file, if any, will be stored), while the remaining items are a path within the HDB (e.g. a partition).

dsave provides roughly the same functionality as the combination of .Q.en and set or .Q.dpft, but in a simpler form.

q)t:flip`sym`price`size!100?'(-10?`3;1.0;10)
q)q:flip`sym`bid`ask`bsize`asize!900?'(distinct t`sym;1.0;1.0;10;10)
q)meta t
c    | t f a
-----| -----
sym  | s    
price| f    
size | j    
q)meta q    
c    | t f a
-----| -----
sym  | s    
bid  | f    
ask  | f    
bsize| j    
asize| j    
q)type each flip t
sym  | 11
price| 9
size | 7
q)type each flip q
sym  | 11
bid  | 9
ask  | 9
bsize| 7
asize| 7
q)`:/tmp/db1 dsave`sym xasc'`t`q
`t`q
q)\l /tmp/db1
q)meta t
c    | t f a
-----| -----
sym  | s   p
price| f    
size | j    
q)meta q
c    | t f a
-----| -----
sym  | s   p
bid  | f    
ask  | f    
bsize| j    
asize| j    
q)type each flip t
sym  | 20
price| 9
size | 7
q)type each flip q
sym  | 20
bid  | 9
ask  | 9
bsize| 7
asize| 7
q)

In the following, the left argument is a list, of which the second item is a partition name.

q)t:flip`sym`price`size!100?'(-10?`3;1.0;10)
q)q:flip`sym`bid`ask`bsize`asize!900?'(distinct t`sym;1.0;1.0;10;10)
q)meta t
c    | t f a
-----| -----
sym  | s    
price| f    
size | j    
q)meta q
c    | t f a
-----| -----
sym  | s    
bid  | f    
ask  | f    
bsize| j    
asize| j    
q)type each flip t
sym  | 11
price| 9
size | 7
q)type each flip q
sym  | 11
bid  | 9
ask  | 9
bsize| 7
asize| 7
q)`:/tmp/db2`2015.01.01 dsave`sym xasc'`t`q
`t`q
q)\l /tmp/db2
q)meta t
c    | t f a
-----| -----
date | d    
sym  | s   p
price| f    
size | j    
q)meta q
c    | t f a
-----| -----
date | d    
sym  | s   p
bid  | f    
ask  | f    
bsize| j    
asize| j    

set, .Q.en, .Q.dpft, .Q.hdpf
Basics: File system