Module graph 

Building a table’s graph sections from the table’s own columns.

This is where the two halves meet. rudb-graph at rank 5 knows what a key map is and knows nothing about a file; the rest of this crate knows how to put an opaque payload in a file and nothing about what one means. Neither of them can build a key map for a real table, because doing that means reading a column back, so it happens here, in the crate that is allowed to see both.

Everything here obeys spec/graph/03-the-file-format.md section 3.1. A column that cannot be mapped is a column with no key map, not an error at open; a section that is stale, torn, or of a form this build does not know is a section that is not there. That is why key_map answers with an Option and not a Result: there is no failure it could report that is not answered by running the query the way it ran before the section existed.

Structs

Built

What building one key map cost and what it bought.

KeyColumn

One column of a committed table, scanned in rid order.

Constants

BUDGET_FLOOR

The size below which a table’s graph sections always fit, whatever the share works out to.

BUDGET_SHARE

The share of a table’s stored column bytes its graph sections are allowed to cost together.

Functions

build_key_map

Builds the key map for one column of a committed table.

build_key_maps

Builds a key map for each of these columns and attaches them all in one commit.

build_key_maps_within

The same, against a budget of share percent of the table’s stored column bytes.

key_map

The key map this table carries for a column, when it carries one this build can use.