icydb-core 0.212.3

IcyDB — A schema-first typed query engine and persistence runtime for Internet Computer canisters
Documentation 
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//! Schema-owned field allocation helpers for DDL-authored field candidates.

use crate::db::schema::{
    AcceptedFieldKind, AcceptedSchemaSnapshot, FieldId, PersistedFieldOrigin,
    PersistedFieldSnapshot, SchemaFieldSlot, SchemaFieldWritePolicy, SchemaHistoricalFill,
    SchemaInsertDefault,
};
use crate::model::field::{FieldStorageDecode, LeafCodec};

/// Field addition candidate resolution failures for SQL DDL-authored schema
/// mutations.
#[derive(Clone, Debug, Eq, PartialEq)]
pub(in crate::db) enum SchemaDdlFieldAdditionCandidateError {
    /// An accepted field already uses the requested SQL column name.
    Duplicate,
    /// The entity cannot allocate another physical row-layout identity.
    RowLayoutVersionExhausted,
}

/// Resolve the accepted name boundary for one SQL DDL field addition before
/// SQL type or default decoding performs work for an already-existing column.
pub(in crate::db) fn resolve_sql_ddl_field_addition_name_candidate(
    accepted_before: &AcceptedSchemaSnapshot,
    name: &str,
) -> Result<(), SchemaDdlFieldAdditionCandidateError> {
    if accepted_before
        .persisted_snapshot()
        .fields()
        .iter()
        .any(|field| field.name() == name)
    {
        return Err(SchemaDdlFieldAdditionCandidateError::Duplicate);
    }

    Ok(())
}

/// Build one DDL-owned additive field candidate with schema-owned ID and slot
/// allocation. SQL DDL supplies author intent; schema mutation code assigns
/// durable catalog identity.
pub(in crate::db) fn build_sql_ddl_field_addition_candidate(
    accepted_before: &AcceptedSchemaSnapshot,
    name: String,
    kind: AcceptedFieldKind,
    nullable: bool,
    default: SchemaInsertDefault,
    storage_decode: FieldStorageDecode,
    leaf_codec: LeafCodec,
) -> Result<PersistedFieldSnapshot, SchemaDdlFieldAdditionCandidateError> {
    resolve_sql_ddl_field_addition_name_candidate(accepted_before, name.as_str())?;

    let introduced_in_layout = accepted_before
        .persisted_snapshot()
        .row_layout()
        .current_version()
        .checked_next()
        .ok_or(SchemaDdlFieldAdditionCandidateError::RowLayoutVersionExhausted)?;
    let historical_fill = match default.slot_payload() {
        Some(payload) => SchemaHistoricalFill::SlotPayload(payload.to_vec()),
        None if nullable => SchemaHistoricalFill::Null,
        None => SchemaHistoricalFill::Reject,
    };

    Ok(PersistedFieldSnapshot::new_with_write_policy_and_origin(
        next_sql_ddl_field_id(accepted_before),
        name,
        next_sql_ddl_field_slot(accepted_before),
        kind,
        Vec::new(),
        nullable,
        introduced_in_layout,
        default,
        historical_fill,
        SchemaFieldWritePolicy::from_model_policies(None, None),
        PersistedFieldOrigin::SqlDdl,
        storage_decode,
        leaf_codec,
    ))
}

fn next_sql_ddl_field_id(accepted_before: &AcceptedSchemaSnapshot) -> FieldId {
    let next = u32::try_from(accepted_before.persisted_snapshot().fields().len())
        .ok()
        .and_then(|count| count.checked_add(1))
        .expect("accepted field IDs should not be exhausted");

    FieldId::new(next)
}

fn next_sql_ddl_field_slot(accepted_before: &AcceptedSchemaSnapshot) -> SchemaFieldSlot {
    accepted_before
        .persisted_snapshot()
        .row_layout()
        .next_unallocated_slot()
}