Trace a column's ancestry or descendants

lineage_upstream() lists every column that feeds into column, following edges transitively; lineage_downstream() lists every column column feeds into. This is the core impact-analysis question ("what breaks if this column changes?") answered directly on the lineage object, without exporting to a graph tool. Passing a table name instead of a column traces from every column of that table at once.

Usage

lineage_upstream(lineage, column)

lineage_downstream(lineage, column)

Arguments

lineage

The result of extract_lineage(), or any list with nodes and edges built with create_table_node() and create_column_edge().

column

A "table.column" string identifying the column to trace from, e.g. "output.total_spent", or a table name to trace from all of that table's columns. Names are matched exactly, never split on dots; a string that is both a column key and a schema-qualified table name (a node "main" with column "silver" alongside a node "main.silver") is read as the column key.

Value

A character vector of "table.column" identifiers, sorted. Empty when the column has no upstream (or downstream) connections. For a table, the table's own columns are not part of the answer.

See also

Other lineage accessors: lineage_check(), lineage_diff(), lineage_edges(), lineage_tables(), lineage_unused()

Examples

lineage <- list(
  nodes = list(
    create_table_node("orders", "amount"),
    create_table_node("daily_totals", "total", table_type = "target")
  ),
  edges = list(
    create_column_edge("orders", "amount", "daily_totals", "total")
  )
)
lineage_upstream(lineage, "daily_totals.total")
#> [1] "orders.amount"
lineage_downstream(lineage, "orders.amount")
#> [1] "daily_totals.total"
lineage_downstream(lineage, "orders")
#> [1] "daily_totals.total"