EXPLAIN

EXPLAIN compiles a statement and returns planning metadata without executing the generated query or applying the mutation.

Syntax

EXPLAIN [(metadata_options)] statement

EXPLAIN [(metadata_options)]
<following statements in the same multi-statement request>

EXPLAIN [(metadata_options)] statement

EXPLAIN [(metadata_options)]
<following statements in the same multi-statement request>

When a statement follows EXPLAIN directly, only that statement is explained. Bare EXPLAIN is the multi-statement form used by tooling to explain the remaining request.

Options

The parenthesized option block is a comma-separated list of flags, key/value options, or option functions.

• FIELDS(...) selects top-level fields such as STAGE, OUTPUT_SCHEMA, FEATURES, and FINAL_NODES.
• FORMAT JSON requests the structured JSON representation.
• MUTATION_DRY_RUN includes the prospective effect of a supported registry mutation.

EXPLAIN (
    FIELDS (STAGE, OUTPUT_SCHEMA, FEATURES)
)
RETURN
    NET_REVENUE := GROSS_REVENUE - REFUNDS
FROM FM.SALES;

The ordinary result shape is one OUTPUT VARCHAR cell containing JSON. Unknown field names and options are rejected rather than silently ignored.

EXPLAIN can prefix another top-level statement, including CREATE, ALTER, or DROP, when that action supports dry-run planning.

See Statement tools and EXPLAIN for reading the output, and Feature metadata for mutation dry-run use cases.