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fix(postgres): read EXPLAIN JSON output as json column #279

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Merged
debba merged 2 commits into from
Jun 4, 2026
Merged

fix(postgres): read EXPLAIN JSON output as json column #279

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fix(postgres): read EXPLAIN JSON output as json column
debba Jun 3, 2026
b87b318
Update src-tauri/src/drivers/postgres/explain.rs
debba Jun 4, 2026
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14 changes: 12 additions & 2 deletions src-tauri/src/drivers/postgres/explain.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -29,8 +29,18 @@ pub async fn explain_query(
return Err("EXPLAIN returned no output".into());
}

// PostgreSQL returns a single row with a single text column containing JSON
let plan_json_str: String = rows[0].try_get(0).map_err(|e| format_pg_error(&e))?;
// `EXPLAIN (FORMAT JSON)` on real PostgreSQL returns a column of type
// `json` (not `text`), so reading it as `String` fails with
// "error deserializing column 0". Read it as a `serde_json::Value` and
// re-serialize. Some Postgres-compatible engines hand back a plain `text`
// column instead, so fall back to reading the raw string in that case.
let plan_json_str = match rows[0].try_get::<_, serde_json::Value>(0) {
Ok(value) => value.to_string(),
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@NewtTheWolf NewtTheWolf Jun 4, 2026

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Nit (non-blocking): this is a triple round-trip — PG sends JSON text → tokio-postgres parses into serde_json::Value → .to_string() re-serializes → parse_postgres_json parses it again. Totally fine for small EXPLAIN output, just flagging in case parse_postgres_json could grow a &serde_json::Value entry point to skip the re-parse. Not worth it unless it's trivial.

Err(json_err) => rows[0].try_get::<_, String>(0).map_err(|e| {
log::debug!("EXPLAIN json read failed ({json_err}); text read also failed");
format_pg_error(&e)
})?,
};

let mut plan = parse_postgres_json(&plan_json_str)?;
plan.original_query = query.to_string();
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