queryplan

const (
	// Name is the snapshot section key.
	Name = "queryplan"

	// EnvFlag is the master flag, and it is off unless it is explicitly
	// turned on: EXPLAIN issues extra statements against the measured
	// database, so it is opt-in rather than opt-out.
	EnvFlag = "ISUTOOLS_EXPLAIN"

	// EnvTop overrides how many digests of one target are explained.
	EnvTop = "ISUTOOLS_EXPLAIN_TOP"

	// DefaultTop is how many SELECT digests per target are selected when
	// EnvTop is unset. It is a selection ceiling, not a promise: the digest
	// loop stops as soon as the per-target budget can no longer fit another
	// EXPLAIN.
	DefaultTop = 10
)

const (
	// SessionBudget bounds session establishment: role neutralisation, grant
	// verification, de-instrumentation, capability probing and USE.
	SessionBudget = 300 * time.Millisecond
	// SampleBudget bounds the single statement that reads every sample.
	SampleBudget = 100 * time.Millisecond
	// PerDigestBudget bounds one EXPLAIN. It is a cutoff, not a reservation:
	// a real EXPLAIN takes single-digit milliseconds, and reserving ten of
	// these would exceed the whole enrich budget on the first target.
	PerDigestBudget = 250 * time.Millisecond
)

const (
	// CodePurposeUnregistered means the target has no PurposeExplain
	// credential. It is never treated as a reason to use another one.
	CodePurposeUnregistered = "explain-purpose-unregistered"
	// CodeUnknownTarget means the registry does not know the target ID the
	// interval was published under.
	CodeUnknownTarget = "explain-unknown-target"
	// CodeNoSchema means there is no schema name that can be bound to
	// WHERE SCHEMA_NAME = ? and quoted into USE.
	CodeNoSchema = "explain-no-schema"
	// CodeUnsupported means the server has no QUERY_SAMPLE_TEXT column, i.e.
	// it is older than MySQL 8.0.17 or is MariaDB.
	CodeUnsupported = "explain-unsupported"
	// CodeRolesActive means active roles could neither be neutralised nor
	// enumerated, so the effective privileges are unknown.
	CodeRolesActive = "explain-roles-active"
	// CodeGrantsTooBroad means the effective privileges include something
	// outside the allowlist.
	CodeGrantsTooBroad = "explain-grants-too-broad"
	// CodeGrantsUnverifiable means SHOW GRANTS could not be read or could not
	// be parsed. An unknown grant line is treated as a dangerous one.
	CodeGrantsUnverifiable = "explain-grants-unverifiable"
	// CodeSessionInstrumented means the session could not be proven
	// uninstrumented, so its own statements would land in the interval the
	// next run measures.
	CodeSessionInstrumented = "explain-session-instrumented"
	// CodeBudgetExhausted means the enrich budget ran out before this
	// target's wave could start. Recorded rather than dropped.
	CodeBudgetExhausted = "explain-budget-exhausted"
	// CodeTargetTimeout means the target's session did start but had not
	// returned when the enrich budget expired, so the capture stopped waiting
	// for it. Unlike CodeBudgetExhausted it points at one connection rather
	// than at the fan-out: statements were issued, and something — a driver
	// that ignores its context, a connection stuck in a syscall, a proxy that
	// never answered — did not come back inside the budget.
	CodeTargetTimeout = "explain-target-timeout"
	// CodeQueryError means a statement of the session sequence failed for a
	// reason none of the codes above describes.
	CodeQueryError = "explain-query-error"
	// CodeNoInterval means sqlrows published no usable interval for the
	// target, so there is nothing to rank digests by.
	CodeNoInterval = "explain-no-interval"
	// CodeNoDigests means the interval holds no SELECT digest worth
	// explaining.
	CodeNoDigests = "explain-no-digests"
	// CodeNoDefaultDatabase means the server answered EXPLAIN with 1046 "No
	// database selected", i.e. the USE step did not take effect. That is a
	// fault of this package rather than of the statement, so it is reported in
	// health as well as on the plan.
	CodeNoDefaultDatabase = "explain-no-default-database"
)

const MaxTop = sqlrows.DigestTextFetchLimit