Target State

A target state represents what you want to exist in an external system. You declare target states in your code; CocoIndex keeps them in sync with your intent — creating, updating, or removing them as needed.

Terminology

A target state is the external thing you want to exist (a file, a row, a table, etc.). A target is the object/API you use to declare those target states (like DirTarget or TableTarget).

CocoIndex treats your declarations as the source of truth: if you stop declaring a target state, CocoIndex will remove it from the external system.

Examples of target states:

• A file in a directory
• A row in a database table
• An embedding vector in a vector store

When your source data changes, CocoIndex compares the newly declared target states with those from the previous run and applies only the necessary changes.

Declaring target states

CocoIndex connectors provide targets with declare_* methods:

# Declare a file target state
dir_target.declare_file(filename="output.html", content=html)

# Declare a row target state
table_target.declare_row(row=DocEmbedding(...))

Where do targets come from?

Target states can be nested — a directory contains files, a table contains rows. The container itself is a target state you declare, and once it's ready, you get a target to declare child target states within it.

Container target states (like a directory or table) are typically top-level — you can declare them directly. Child target states (like files or rows) require the container to be ready first.

Connectors provide convenience methods that mount the container and return a ready-to-use target in one step:

Example: writing a file to a directory

For simple cases where each processing component writes a single file, you can declare the file directly:

from cocoindex.connectors import localfs

# Declare a single file target state directly
localfs.declare_file(outdir / "output.html", html, create_parent_dirs=True)

When you need a DirTarget to declare multiple files, use the connector's convenience method:

# Mount a directory target, get a ready-to-use DirTarget
dir_target = await localfs.mount_dir_target(outdir)

# Declare child target states (files)
dir_target.declare_file(filename="output.html", content=html)

Example: writing a row to PostgreSQL

from cocoindex.connectors import postgres

# Mount a table target, get a ready-to-use TableTarget
table = await target_db.mount_table_target(
    table_name="doc_embeddings",
    table_schema=await postgres.TableSchema.from_class(
        DocEmbedding, primary_key=["id"]
    ),
)

# Declare a child target state (a row)
table.declare_row(row=DocEmbedding(...))

These convenience methods wrap mount_target(), which automatically derives the component path from the target's globally unique key. See Processing Component for more on mounting APIs.

Type safety

Targets like DirTarget and TableTarget have two statuses: pending (just created) and resolved (after the container target state is ready). The type system tracks this — if you try to use a pending target before it's resolved, type checkers like mypy will flag the error.

How CocoIndex syncs target states

Under the hood, CocoIndex compares your declared target states with the previous run and applies the minimal changes needed:

Target State	CocoIndex's Action
	On first declaration	When declared differently	When no longer declared
A database table	Create the table	Alter the table	Drop the table
A row in a database table	Insert the row	Update the row	Delete the row
A file in a directory	Create the file	Update the file	Delete the file

CocoIndex ensures containers exist before their contents are added, and properly cleans up contents when the container changes.

Generic target state APIs

For cases where connector-specific APIs don't cover your needs, CocoIndex provides generic APIs:

• declare_target_state() — declare a leaf target state
• declare_target_state_with_child() — declare a target state that provides child target states

These are exported from cocoindex and used internally by connectors. For defining custom targets, see Custom Target States Connector.