id,node_id,number,title,user,state,locked,assignee,milestone,comments,created_at,updated_at,closed_at,author_association,pull_request,body,repo,type,active_lock_reason,performed_via_github_app,reactions,draft,state_reason
642651572,MDU6SXNzdWU2NDI2NTE1NzI=,860,Plugin hook for instance/database/table metadata,9599,closed,0,,,10,2020-06-21T22:20:25Z,2022-01-13T22:21:42Z,2021-06-26T22:56:28Z,OWNER,,"I'm not happy with how `metadata.(json|yaml)` keeps growing new features. Rather than having a single plugin hook for all of `metadata.json` I'm going to split out the feature that shows actual real metadata for tables and databases - `source`, `license` etc - into its own plugin-powered mechanism.

_Originally posted by @simonw in https://github.com/simonw/datasette/issues/357#issuecomment-647189045_",107914493,issue,,,"{""url"": ""https://api.github.com/repos/simonw/datasette/issues/860/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,completed
642572841,MDU6SXNzdWU2NDI1NzI4NDE=,859,Database page loads too slowly with many large tables (due to table counts),3243482,open,0,,,21,2020-06-21T14:23:17Z,2021-08-25T21:59:55Z,,CONTRIBUTOR,,"Hey,
I have a database that I save in HTML from couple of web scrapers. There are around 200k+, 50+ rows in a couple of tables, with sqlite file weighing around 600MB.

The app runs on a VPS with 2 core CPU, 4GB RAM and refreshing database page regularly takes more than 10 seconds. I was suspecting that counting tables was the culprit, but manually running `select count(*) from table_name` for the largest table finishes under a second.

I've looked at the source code. There's a check for index page for mutable databases larger than 100MB
https://github.com/simonw/datasette/blob/799c5d53570d773203527f19530cf772dc2eeb24/datasette/views/index.py#L15

but this check is not performed for database page. 
I've manually crippled `Database::table_counts` method
```py
async def table_counts(self, limit=10):
    if not self.is_mutable and self.cached_table_counts is not None:
        return self.cached_table_counts
    # Try to get counts for each table, $limit timeout for each count
    counts = {}
    for table in await self.table_names():
        try:
            # table_count = (
            #     await self.execute(
            #         ""select count(*) from [{}]"".format(table),
            #         custom_time_limit=limit,
            #     )
            # ).rows[0][0]
            counts[table] = 10 # table_count
        # In some cases I saw ""SQL Logic Error"" here in addition to
        # QueryInterrupted - so we catch that too:
        except (QueryInterrupted, sqlite3.OperationalError, sqlite3.DatabaseError):
            counts[table] = None
    if not self.is_mutable:
        self.cached_table_counts = counts
    return counts
```

now the page loads in <100ms.

Is it possible to apply size check on database page too?

<details>
<summary>
/-/versions output
</summary>
<pre>
{
    ""python"": {
        ""version"": ""3.8.0"",
        ""full"": ""3.8.0 (default, Oct 28 2019, 16:14:01) \n[GCC 8.3.0]""
    },
    ""datasette"": {
        ""version"": ""0.44""
    },
    ""asgi"": ""3.0"",
    ""uvicorn"": ""0.11.5"",
    ""sqlite"": {
        ""version"": ""3.22.0"",
        ""fts_versions"": [
            ""FTS5"",
            ""FTS4"",
            ""FTS3""
        ],
        ""extensions"": {
            ""json1"": null
        },
        ""compile_options"": [
            ""COMPILER=gcc-7.4.0"",
            ""ENABLE_COLUMN_METADATA"",
            ""ENABLE_DBSTAT_VTAB"",
            ""ENABLE_FTS3"",
            ""ENABLE_FTS3_PARENTHESIS"",
            ""ENABLE_FTS3_TOKENIZER"",
            ""ENABLE_FTS4"",
            ""ENABLE_FTS5"",
            ""ENABLE_JSON1"",
            ""ENABLE_LOAD_EXTENSION"",
            ""ENABLE_PREUPDATE_HOOK"",
            ""ENABLE_RTREE"",
            ""ENABLE_SESSION"",
            ""ENABLE_STMTVTAB"",
            ""ENABLE_UNLOCK_NOTIFY"",
            ""ENABLE_UPDATE_DELETE_LIMIT"",
            ""HAVE_ISNAN"",
            ""LIKE_DOESNT_MATCH_BLOBS"",
            ""MAX_SCHEMA_RETRY=25"",
            ""MAX_VARIABLE_NUMBER=250000"",
            ""OMIT_LOOKASIDE"",
            ""SECURE_DELETE"",
            ""SOUNDEX"",
            ""TEMP_STORE=1"",
            ""THREADSAFE=1""
        ]
    }
}
</pre>
</details>",107914493,issue,,,"{""url"": ""https://api.github.com/repos/simonw/datasette/issues/859/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,
642652808,MDU6SXNzdWU2NDI2NTI4MDg=,861,Script to generate larger SQLite test files,9599,closed,0,,,3,2020-06-21T22:30:58Z,2020-06-23T03:44:18Z,2020-06-23T03:44:18Z,OWNER,,"> I'll write a little script which generates a 300MB SQLite file with a bunch of tables with lots of randomly generated rows in to help test this.
> 
> Having a tool like that which can generate larger databases with different gnarly performance characteristics will be useful for other performance work too.
_Originally posted by @simonw in https://github.com/simonw/datasette/issues/859#issuecomment-647189948_",107914493,issue,,,"{""url"": ""https://api.github.com/repos/simonw/datasette/issues/861/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,completed