Filter rows of a vectra query
Details
Filter uses zero-copy selection vectors: matching rows are indexed without
copying data. Multiple conditions are combined with &. Supported
expression types: arithmetic (+, -, *, /, %%), comparison
(==, !=, <, <=, >, >=), boolean (&, |, !), is.na(),
and string functions (nchar(), substr(), grepl() with fixed patterns).
NA comparisons return NA (SQL semantics). Use is.na() to filter NAs
explicitly.
This is a streaming operation (constant memory per batch).