List of read options in Envision

List of read options












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The read statement in Envision offers the possibility to load one or more files into a table. Below, we gather the different options relating to the read statement.


Syntax overview

The usual syntax for reading a file in Envision is as follows:
read "/sample/Lokad_Orders.csv.gz" as Orders with
  "Order Date" as OrderDate : date
  "Quantity" as Qty
The text which comes just after the read keyword is referred to as the path. The path is intended to match the files that exist in the file storage associated with a given Lokad account.

The columns are not required to be explicitly listed after the with keyword. In this case, the columns are available within the Envision script as long as the column names are valid variable names (for example, no spaces allowed in the column name). The primary purpose of the keyword as is to rename both tables and columns.

If the as option that follows the read is omitted, then, Envision reads this file as part of the items table.

Reading multiple files

It is possible to read multiple files at once through the use of the wildcard [*] in the specified path:
read "/sample/Lokad_Orders*.gz" as Orders
Multiple wildcards are authorized.

Filter one file among many

In order to restrict the set of files originally captured by the wildcard to a single file, the read statement supports 3 distinct modifiers:
  • min: only the first file within the set is retained, ordering is based on the file names.
  • max: only the last file within the set is retained, ordering is based on the file names.
  • latest: only the most recently updated file within the set is retained.

Using the above modifiers can be done as follows:
read max "/sample/Lokad_Orders*.gz" as Orders

Filter many files among many

In order to restrict the set of files originally captured by the wildcard to a single set of files that share the same folder, the read statement can use the percentage sign (%) - one at most - to indicate the folder match of interest.
read max "/%/Lokad_Orders*.gz" as Orders

The read statement will capture all the files that match the folder as restricted by the modifier. As a folder does not have a last updated date in Lokad, only the min and max modifiers are allowed when the percentage sign is present. Conversely, when the percentage sign is present, one read modifier should be present too.

Table-level options

Multiple options are supported in relation to the read statement:
  • skip (number): Indicates how many lines should be skipped at the beginning of the file while the file is being read. If omitted, the default value is zero.
  • separator (text): Indicates the separator between cell values to be used when parsing the file. If omitted, Envision will use auto-detection heuristics to determine the most likely separator.
  • quotes (boolean): If false is used, the extreme quotes found in a cell token are considered to be part of the token and not escaped. If omitted, the default value is true and Envision escapes extreme quotes, as is usually done with CSV (comma-separated values) files.
  • encoding (text): The text encoding to be used while parsing the file. The accepted encoding values are: UTF-8, UTF-16 and latin1. If omitted, Envision will use auto-detection heuristics to determine the most likely encoding.

The script below illustrates how the above options can be specified:
read "/sample/Lokad_Orders.csv.gz" skip:0 separator:"\t" quotes:false encoding:"UTF-8"

Table type options

Envision offers the possibility to define the primary keys for a table, by listing them between parentheses right after specifying the table name. There are only 7 primary key combinations that are allowed:
read "a.csv" as A[*]
read "b.csv" as B[Id]
read "c.csv" as C[Id, *]
read "d.csv" as D[Date]
read "e.csv" as E[Date, *]
read "f.csv" as F[Id, Date]
read "g.csv" as G[Id, Date, *]

The table type option can be omitted. In this case, the default type applied is [Id, Date, *].

Column-level options

Multiple options are also supported for each column to be read:

  • The data type of the column, which can be text, number, date, bool or distribution. The data type is introduced after a colon (:) that follows the column name.
  • date: the date format string
  • number: the number format string

The following script illustrates the usage of the column options:
read "/sample/Lokad_Orders.csv.gz" as Orders with
  date:"dd-MM-yyy" as OrderDate : date
  number:"1,000.00" as Qty

Specifying the columns is optional. Specifying the data type of a column is also optional even if the column is specified. When data type is not specified with the read statement, the column data type is inferred from usage within the Envision script.

Distributions are an advanced data type that is only supported by Lokad's Ionic file format.

Number options

The number format string imitates the actual desired output for the numbers:
  • The character after the initial 1 is the thousand separator. It can be omitted.
  • The character before the last zeroes is the decimal separator. It can be omitted.

Date options

The format string for the date option can be built from the following tokens:

  • d: day of the month from 1 through to 31
  • dd: same as d but 0 prefixed
  • ddd: Abbreviated day of the week (i.e. Mon, Tue...)
  • dddd: Full day of the week (Monday...)
  • MM: Month number from 1 through to 12
  • MMM: Abbreviated name of the month (Jun)
  • MMMM: Full name of the month (June)
  • yy: Year number from 00 to 99; ignore the hundreds and thousands
  • yyyy: year with four digits