List of read options
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
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 that 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.
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. The wildcard can replace any string of characters, except those containing a
/. It may be used in the file name as well as in a folder name, and may include the file format. An empty string would also match the wildcard. Finally, multiple wildcards within the same path are supported. As an example,
read "/sample/Lokad_Orders*" as Orders
could match “/sample/Lokad_Orders-2018-07-25.csv.gz” as well as “/sample/Lokad_Orders.tsv”.
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, filtering can be done as follows:
read max "/sample/Lokad_Orders*.gz" as Orders
In addition, Envision supports the possibility of reading a specified number of files. This can be expressed by adding a literal positive integer just after the wildcard filter (e.g.,
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
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
max modifiers are allowed when the percentage sign is present. Conversely, when the percentage sign is present, one
read modifier should be present too.
Multiple options are supported in relation to the
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.
trueis 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
falseand 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:
latin1. If omitted, Envision will use auto-detection heuristics to determine the most likely encoding.
headers(text): column headers can be specified within Envision, if they are missing in the input file.
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" headers:"OrderDate, Qty"
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, *].
Multiple options are also supported for each column to be read:
- The data type of the column, which can be
distribution. The data type is introduced after a colon (
:) that follows the column name.
date: the date format string
number: the number format string
const: a constant value (of type
number) to attribute to a column that does not exist in the file; this is particularly helpful when reading multiple files as one single table (see also Syntax to read files)
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 const(true) as IsClosed
Specifying the columns is optional. Specifying a column’s data type 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.
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.
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