Create a 'tiledb_query_condition' object from an expression

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

Value

A tiledb_query_condition object

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.

Examples

if (FALSE) { # \dontrun{
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)
)[]
} # }