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Implemented cursor-based pagination for table view

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Closes #5
This commit is contained in:
Simon Willison 2017-11-10 12:41:14 -08:00
commit 21c9c04310
4 changed files with 72 additions and 18 deletions
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70
datasette/app.py
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@ -14,10 +14,11 @@ import json
import hashlib
import time
from .utils import (
build_where_clause,
build_where_clauses,
CustomJSONEncoder,
InvalidSql,
path_from_row_pks,
path_with_added_args,
compound_pks_from_path,
sqlite_timelimit,
validate_sql_select,
@ -78,6 +79,7 @@ class BaseView(HTTPMethodView):
self.files = datasette.files
self.jinja = datasette.jinja
self.executor = datasette.executor
self.page_size = datasette.page_size
self.cache_headers = datasette.cache_headers
def redirect(self, request, path):
@ -270,16 +272,52 @@ class TableView(BaseView):
select = '*'
order_by = ', '.join(pks)
if request.args:
where_clause, params = build_where_clause(request.args)
sql = 'select {} from "{}" where {} order by {} limit 50'.format(
select, table, where_clause, order_by
)
# Special args start with _ and do not contain a __
# That's so if there is a column that starts with _
# it can still be queried using ?_col__exact=blah
special_args = {}
other_args = {}
for key, value in request.args.items():
if key.startswith('_') and '__' not in key:
special_args[key] = value[0]
else:
other_args[key] = value[0]
if other_args:
where_clauses, params = build_where_clauses(other_args)
else:
sql = 'select {} from "{}" order by {} limit 50'.format(
select, table, order_by
)
params = []
where_clauses = []
params = {}
after = special_args.get('_after')
if after:
if use_rowid:
where_clauses.append(
'rowid > :p{}'.format(
len(params),
)
)
params['p{}'.format(len(params))] = after
else:
pk_values = compound_pks_from_path(after)
if len(pk_values) == len(pks):
param_counter = len(params)
for pk, value in zip(pks, pk_values):
where_clauses.append(
'"{}" > :p{}'.format(
pk, param_counter,
)
)
params['p{}'.format(param_counter)] = value
param_counter += 1
where_clause = ''
if where_clauses:
where_clause = 'where {}'.format(' and '.join(where_clauses))
sql = 'select {} from "{}" {} order by {} limit {}'.format(
select, table, where_clause, order_by, self.page_size + 1,
)
rows = await self.execute(name, sql, params)
@ -290,20 +328,27 @@ class TableView(BaseView):
rows = list(rows)
info = ensure_build_metadata(self.files)
total_rows = info[name]['tables'].get(table)
after = None
after_link = None
if len(rows) > self.page_size:
after = path_from_row_pks(rows[-2], pks, use_rowid)
after_link = path_with_added_args(request, {'_after': after})
return {
'database': name,
'table': table,
'rows': rows,
'rows': rows[:self.page_size],
'total_rows': total_rows,
'columns': columns,
'primary_keys': pks,
'sql': sql,
'sql_params': params,
'after': after,
}, lambda: {
'database_hash': hash,
'use_rowid': use_rowid,
'row_link': lambda row: path_from_row_pks(row, pks, use_rowid),
'display_columns': display_columns,
'after_link': after_link,
}
@ -381,13 +426,14 @@ def resolve_db_name(files, db_name, **kwargs):
class Datasette:
def __init__(self, files, num_threads=3, cache_headers=True):
def __init__(self, files, num_threads=3, cache_headers=True, page_size=50):
self.files = files
self.num_threads = num_threads
self.executor = futures.ThreadPoolExecutor(
max_workers=num_threads
)
self.cache_headers = cache_headers
self.page_size = page_size
def app(self):
app = Sanic(__name__)