parse_query_condition: Create a 'tiledb_query_condition' object from an expression

In tiledb: Modern Database Engine for Complex Data Based on Multi-Dimensional Arrays

Create a 'tiledb_query_condition' object from an expression

Description

The grammar for query conditions is at present constraint to eight operators (">", ">=", "<", "<=", "==", "!=", "%in%", "%nin%"), and three boolean operators ("&&", also as "&", ("||", also as "|", and "!" for negation. Note that we locally define "%nin%" as Negate() call around %in%) which extends R a little for this use case.

Usage

parse_query_condition(
  expr,
  ta = NULL,
  debug = FALSE,
  strict = TRUE,
  use_int64 = FALSE
)

Arguments

expr	An expression that is understood by the TileDB grammar for query conditions.
ta	A tiledb_array object that the query condition is applied to; this argument is optional in some cases but required in some others.
debug	A boolean toogle to enable more verbose operations, defaults to 'FALSE'.
strict	A boolean toogle to, if set, errors if a non-existing attribute is selected or filtered on, defaults to 'TRUE'; if 'FALSE' a warning is shown by execution proceeds.
use_int64	A boolean toggle to switch to integer64 if integer is seen, default is false to remain as a default four-byte int

Details

Expressions are parsed locally by this function. The debug=TRUE option may help if an issue has to be diagnosed. In most cases of an errroneous parse, it generally helps to supply the tiledb_array providing schema information. One example are numeric and integer columns where the data type is difficult to guess. Also, when using the "%in%" or "%nin%" operators, the argument is mandatory.

Value

A tiledb_query_condition object

Examples

## Not run: 
uri <- "mem://airquality"    # change to on-disk for persistence
fromDataFrame(airquality, uri, col_index=c("Month", "Day"))  # dense array
## query condition on dense array requires extended=FALSE
tiledb_array(uri, return_as="data.frame", extended=FALSE,
             query_condition=parse_query_condition(Temp > 90))[]

## End(Not run)

tiledb documentation built on Oct. 4, 2024, 5:06 p.m.