Function to_parquet 

pub fn to_parquet(
    dumps: &[Loaded],
    output: &Path,
    host: &str,
    zstd_level: i32,
) -> Result<usize>

Writes the records of one or more loaded dumps to output as one sparse-wide Parquet table. Returns the total row count. host overrides the dumps’ host label in the footer when non-empty. zstd_level is the zstd compression level (1–22).

Two side effects beyond the Parquet rows, both carrying the assembled query DDL (Tier-1 views generated from the registry + the dumps’ registered Tier-2 view sets, deduped by content): the path-independent DDL is embedded in the Parquet footer under key backbeat.views, and the same DDL — prefixed with a bootstrap that binds the base events view to this Parquet — is written to a <output>.views.sql sidecar (see [sidecar_path]), overwriting any existing file at that path. See crate::views.