Enum IfExists 

pub enum IfExists {
    Error,
    Append,
    Truncate,
    Skip,
    Upsert,
}

What to do when the target table already exists and is non-empty.

Variants

Error

Refuse to copy. Pre-flights the target with SELECT 1 ... LIMIT 1 before issuing any source SELECT.

Append

Insert alongside existing rows. UNIQUE/PK conflicts surface as driver errors and abort the run with already-committed batches still present on the target.

Truncate

DELETE FROM <tbl> then insert. Destructive. Wrapped together with the first batch in a backend-aware transaction so a transient failure of the first INSERT cannot leave the target wiped + empty.

Skip

Insert rows whose primary key does not yet exist on the target; silently skip rows whose PK is already present. PG/SQLite use ON CONFLICT (pk) DO NOTHING, MySQL uses INSERT IGNORE, MSSQL/Oracle use a MERGE … WHEN NOT MATCHED statement.

Requires conflict columns on the destination table — either via a declared primary key, or via the --key COL[,COL...] override. Tables without either raise a hard error.

Upsert

Insert rows whose primary key does not yet exist; update all non-PK columns when the PK already exists. PG/SQLite use ON CONFLICT (pk) DO UPDATE SET col = EXCLUDED.col, MySQL uses INSERT … ON DUPLICATE KEY UPDATE col = VALUES(col), MSSQL/Oracle use a full MERGE with both branches.

Requires a declared primary key on the destination table; see Skip for the no-PK behaviour.

Implementations

impl IfExists

pub fn parse(s: &str) -> Option<Self>

Parse a strategy name (case-insensitive). Recognised: error, append, truncate, skip, upsert.

pub fn resolves_conflicts(self) -> bool

True for the two PK-driven conflict-resolution strategies. Used by run_copy to look up the destination PK once up front and to force the dispatcher onto the generic INSERT path (the native bulk loaders carry no conflict semantics).

Trait Implementations

impl Clone for IfExists

fn clone(&self) -> IfExists

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for IfExists

impl Debug for IfExists

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for IfExists

fn default() -> IfExists

Returns the “default value” for a type.

impl Eq for IfExists

impl PartialEq for IfExists

fn eq(&self, other: &IfExists) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl StructuralPartialEq for IfExists