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Column-level lineage

Source: R/analysis.R
sql_lineage.Rd

Traces each output column of a query back to the tables and expressions it is derived from, following CTEs, subqueries and set operations.

Usage

sql_lineage(sql, dialect = "generic", schema = NULL, column = NULL)

Arguments

sql

A single character string with one or more SQL statements (separated by ;).

dialect

Dialect used for parsing.

schema

Optional schema specification (see as_polyglot_schema()); improves resolution of unqualified or ambiguous columns.

column

Optional single column name. By default, lineage is computed for every output column of the query.

Value

A polyglot_lineage object: a list with one entry per column, each containing

  • column — the output column name;

  • sources — character vector of source tables feeding this column;

  • tree — the lineage graph as nested lists with fields name, source_name, source_kind ("Table", "Cte", "DerivedTable", ...), expression (the SQL of the node's expression) and downstream.

Examples

sql_lineage("SELECT a + b AS total FROM t")
#> <polyglot_lineage> 1 column (generic)
#> total ← t
sql_lineage(
  "WITH base AS (SELECT id, amount FROM payments)
   SELECT id, amount * 2 AS doubled FROM base"
)
#> <polyglot_lineage> 2 columns (generic)
#> id ← payments
#> doubled ← payments