---
title: "pg_typeof"
slug: "dev-database-reference-sql-functions-utility-pg-typeof"
updated: 2026-10-30T18:18:51Z
published: 2026-10-30T18:18:51Z
canonical: "docs.vastdata.com/dev-database-reference-sql-functions-utility-pg-typeof"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://docs.vastdata.com/llms.txt
> Use this file to discover all available pages before exploring further.

# pg_typeof

*Applies to VAST Cluster 5.5.*

*[Functions](/develop/docs/dev-database-reference-sql-functions-index) › [Session and utility functions](/develop/docs/dev-database-reference-sql-functions-utility) › Types.* Returns the SQL type of its argument as lower-case text, such as `bigint`, `varchar` or `decimal(10,2)`. It's the lower-case form of [typeof](/develop/docs/dev-database-reference-sql-functions-conditional-and-cast-typeof); `pg_catalog.pg_typeof` is the same function.

## Syntax

```
pg_typeof(expression)
pg_catalog.pg_typeof(expression)
```

| Argument | Type | Description |
| --- | --- | --- |
| `expression` | Any type | A column, a literal or any expression. |

**Returns:** `VARCHAR`.

## Set up the examples

The examples connect with the ADBC driver, as in [VAST Query Engine (ADBC)](/develop/docs/dev-database-integrations-adbc), and work in a schema called `docs_sql_fn_utility_pg_typeof`. Set `QE_ENDPOINT`, `AWS_ACCESS_KEY_ID`, `AWS_SECRET_ACCESS_KEY` and `VASTDB_BUCKET` ([SQL reference](/develop/docs/dev-database-reference-sql-index#example-connect-and-use-a-transaction)), and run the blocks in order in one Python session. Below each block is the output you should see.

This block connects, defines the `run()` and `plan()` helpers, and creates a table of two items with columns of ten types. The second row has no values:

```
import os
import re

import adbc_driver_manager
import adbc_driver_manager.dbapi as dbapi
import adbc_driver_vastdb

BUCKET = os.environ["VASTDB_BUCKET"]
SCHEMA = f'"{BUCKET}/docs_sql_fn_utility_pg_typeof"'

conn = dbapi.connect(
    driver=adbc_driver_vastdb.get_driver_path(),
    db_kwargs={
        "vast.db.endpoint": os.environ["QE_ENDPOINT"],
        "vast.db.access_key": os.environ["AWS_ACCESS_KEY_ID"],
        "vast.db.secret_key": os.environ["AWS_SECRET_ACCESS_KEY"],
    },
    autocommit=True,
)

def server_message(e):
    """The server's message in a driver error, without the request ID or the echoed statement."""
    text = re.sub(r"\[req=0x[0-9a-f]+\]: ", "", str(e))
    found = (re.search(r'message: "(.*?)", request_id', text, re.S)
             or re.search(r"description: (.*)\)", text, re.S))
    message = found.group(1) if found else text.strip().splitlines()[-1]
    message = re.sub(r"^Plan query: '.*?' failed with: ", "", message, flags=re.S)
    message = re.split(r"\\n|\n", message)[0].replace('\\"', '"')
    return message.replace(BUCKET, "<bucket>")

def run(sql):
    """Run one statement. Print the rows it returns, or the error."""
    try:
        with conn.cursor() as cur:
            cur.execute(sql)
            rows = cur.fetchall() if cur.description else []
    except (adbc_driver_manager.Error, OSError) as e:
        print(f"{type(e).__name__}: {server_message(e)}")
    else:
        print(rows)

def plan(sql):
    """Print the plan without its ~N Rows lines: the table's row count, which can still be 0 just after an insert."""
    with conn.cursor() as cur:
        cur.execute("EXPLAIN " + sql)
        steps = cur.fetchall()[0][1]
    print("\n".join(line for line in steps.splitlines() if "Rows" not in line))

TABLE = f"{SCHEMA}.items"
run(f"CREATE SCHEMA IF NOT EXISTS {SCHEMA}")
run(f"CREATE TABLE IF NOT EXISTS {TABLE} (id BIGINT, name VARCHAR, price DECIMAL(10,2), score DOUBLE, "
    "tags VARCHAR[], attrs STRUCT(a INTEGER, b VARCHAR), added DATE, seen TIMESTAMP, ok BOOLEAN, raw BLOB)")
run(f"INSERT INTO {TABLE} VALUES "
    "(1, 'lamp', 2.50, 0.5, ['home'], {'a': 1, 'b': 'x'}, DATE '2026-10-16', "
    "TIMESTAMP '2026-10-16 12:34:56', true, '\\xAA'::BLOB), "
    "(2, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL)")
```

```
[]
[]
[(2,)]
```

## What it does

`pg_typeof` names the type the Query Engine gives its argument, in lower case:

| Argument | Result |
| --- | --- |
| A `BIGINT` column | `bigint` |
| A `DECIMAL(10,2)` column | `decimal(10,2)` |
| A `VARCHAR[]` column | `varchar[]` |
| A `STRUCT(a INTEGER, b VARCHAR)` column | `struct(a integer, b varchar)` |
| An integer literal, `42` | `integer` |
| A decimal literal, `1.5` | `decimal(2,1)` |
| `1e300` | `double` |
| `1 + 1.5` | `decimal(12,1)` |
| `now()` | `timestamp with time zone` |
| `INTERVAL 1 DAY` | `interval` |
| `[1, NULL, 3]`, `[[1, 2], [3]]` | `integer[]`, `integer[][]` |
| `MAP {&apos;k&apos;: &apos;v&apos;}` | `map(varchar, varchar)` |
| `&apos;{}&apos;::JSON` | `json` |

The type depends only on the expression, not on the value: a NULL in a `BIGINT` column is still `bigint`.

```
run(f"SELECT id, pg_typeof(id), pg_typeof(price), pg_typeof(tags), pg_typeof(attrs) FROM {TABLE} ORDER BY id LIMIT 10")
run("SELECT pg_typeof(42), pg_typeof(1.5), pg_typeof(1e300), pg_typeof(1 + 1.5), pg_typeof(now())")
run("SELECT pg_typeof(INTERVAL 1 DAY), pg_typeof([1, NULL, 3]), pg_typeof([[1, 2], [3]]), "
    "pg_typeof(MAP {'k': 'v'}), pg_typeof('{}'::JSON)")
```

```
[(1, 'bigint', 'decimal(10,2)', 'varchar[]', 'struct(a integer, b varchar)'), (2, 'bigint', 'decimal(10,2)', 'varchar[]', 'struct(a integer, b varchar)')]
[('integer', 'decimal(2,1)', 'double', 'decimal(12,1)', 'timestamp with time zone')]
[('interval', 'integer[]', 'integer[][]', 'map(varchar, varchar)', 'json')]
```

## NULLs and edge cases

| Input | Result |
| --- | --- |
| `NULL` (an untyped NULL) | `&quot;null&quot;`, with the double quotes |
| `[]` (an empty list) | `&quot;null&quot;[]` |
| `{&apos;a&apos;: NULL}` | `struct(a &quot;null&quot;)` |
| `&apos;NaN&apos;::DOUBLE` | `double` |
| `pg_catalog.pg_typeof(&apos;abc&apos;)` | `varchar` |

```
run("SELECT pg_typeof(NULL), pg_typeof([]), pg_typeof({'a': NULL}), pg_typeof(NULL::BIGINT)")
run("SELECT pg_typeof('NaN'::DOUBLE), pg_catalog.pg_typeof('abc')")
```

```
[('"null"', '"null"[]', 'struct(a "null")', 'bigint')]
[('double', 'varchar')]
```

## Examples

The type of every column of the table, read from one row:

```
run(f"SELECT pg_typeof(name), pg_typeof(score), pg_typeof(added), pg_typeof(seen), pg_typeof(ok), "
    f"pg_typeof(raw) FROM {TABLE} WHERE id = 1")
```

```
[('varchar', 'double', 'date', 'timestamp', 'boolean', 'blob')]
```

Check what type an expression produces before you store it, for example the result of a division:

```
run("SELECT pg_typeof(7 / 2), pg_typeof(7 // 2), pg_typeof(2 ** 70)")
```

```
[('double', 'integer', 'double')]
```

## How it runs in VAST

The Query Engine runs on the cluster's CNodes, and a query on a table starts with a scan in VAST DataBase (`VAST_SCAN`). The type of a column or an expression is fixed when the query is planned, so `pg_typeof` doesn't need the rows: in `WHERE`, a condition such as `pg_typeof(price) = &apos;decimal(10,2)&apos;` is settled while the query is planned. The plan has no `FILTER` step, and the condition keeps every row or none:

```
plan(f"SELECT id FROM {TABLE} WHERE pg_typeof(price) = 'decimal(10,2)'")
run(f"SELECT id FROM {TABLE} WHERE pg_typeof(price) = 'decimal(10,2)' ORDER BY id LIMIT 10")
```

```
┌───────────────────────────┐
│         VAST_SCAN         │
│    ────────────────────   │
│    Function: VAST_SCAN    │
│      Projections: id      │
│                           │
└───────────────────────────┘
[(1,), (2,)]
```

## Make it faster

- **Read the types of a table with `DESCRIBE`.** It lists every column and its type:

```
run(f"DESCRIBE {TABLE}")
```

```
[('id', 'BIGINT', 'YES', None, None, None), ('name', 'VARCHAR', 'YES', None, None, None), ('price', 'DECIMAL(10,2)', 'YES', None, None, None), ('score', 'DOUBLE', 'YES', None, None, None), ('tags', 'VARCHAR[]', 'YES', None, None, None), ('attrs', 'STRUCT(a INTEGER, b VARCHAR)', 'YES', None, None, None), ('added', 'DATE', 'YES', None, None, None), ('seen', 'TIMESTAMP', 'YES', None, None, None), ('ok', 'BOOLEAN', 'YES', None, None, None), ('raw', 'BLOB', 'YES', None, None, None)]
```

- **Add `LIMIT 1`** when you read types from a table with `pg_typeof`: every row has the same answer.

## Limitations and errors

- **A NULL without a type is named `&quot;null&quot;`,** with the double quotes; so is the element type of an empty list. Cast the value to give it a type.
- **The names are lower case.** Compare them with lower-case text, such as `&apos;bigint&apos;`, or use [typeof](/develop/docs/dev-database-reference-sql-functions-conditional-and-cast-typeof) for the upper-case names.

## Similar functions

| Function | Result for `1` | for `&apos;a&apos;` | for `[1]` | for `NULL` |
| --- | --- | --- | --- | --- |
| `pg_typeof` | `integer` | `varchar` | `integer[]` | `&quot;null&quot;` |
| [typeof](/develop/docs/dev-database-reference-sql-functions-conditional-and-cast-typeof) | `INTEGER` | `VARCHAR` | `INTEGER[]` | `&quot;NULL&quot;` |

```
run("SELECT pg_typeof(1), typeof(1), pg_typeof('a'), typeof('a'), pg_typeof([1]), typeof([1]), "
    "pg_typeof(NULL), typeof(NULL)")
```

```
[('integer', 'INTEGER', 'varchar', 'VARCHAR', 'integer[]', 'INTEGER[]', '"null"', '"NULL"')]
```

Clean up:

```
run(f"DROP TABLE IF EXISTS {TABLE}")
run(f"DROP SCHEMA IF EXISTS {SCHEMA}")
conn.close()
```

```
[]
[]
```

## See also

- [typeof](/develop/docs/dev-database-reference-sql-functions-conditional-and-cast-typeof).
- [Functions](/develop/docs/dev-database-reference-sql-functions-index): all the function families.
- [EXPLAIN](/develop/docs/dev-database-reference-sql-explain): how to read a plan.