postgres_metrics.metrics module

class postgres_metrics.metrics.AvailableExtensions(ordering=None)[source]

Bases: Metric

PostgreSQL can be extended by installing extensions with the CREATE EXTENSION command. The list of available extensions on each database is shown below.

description = 'PostgreSQL can be extended by installing extensions with the CREATE EXTENSION command. The list of available extensions on each database is shown below.'

get_record_style(record)[source]

Given a single record from MetricResult, decide how to style it. Most likely to be used with the template tag record_style().

By default, django-postgres-metrics supports for styling classes:

ok
warning
critical
info

Override this method and return one of the above strings or None to apply the given style to the entire record. In the Django Admin this will highlight the entire row.

label = 'Available Extensions': The label is what is used in the Django Admin views. Consider making this string translateable.

ordering = '1': The default ordering that should be applied to the SQL query by default. This needs to be a valid ordering string as defined on parsed_ordering.

permission_key = 'postgres_metrics.can_view_metric_available_extensions'

permission_name = 'can_view_metric_available_extensions'

slug = 'available-extensions': A URL safe representation of the label and unique across all metrics.

sql = '\n SELECT\n name,\n default_version,\n installed_version,\n comment\n FROM\n pg_available_extensions\n {ORDER_BY}\n ;\n ': The actual SQL statement that is being used to query the database. In order to make use of the ordering, include the string {ORDER_BY} in the query as necessary. For details on that value see get_order_by_clause().

class postgres_metrics.metrics.CacheHits(ordering=None)[source]

Bases: Metric

The typical rule for most applications is that only a fraction of its data is regularly accessed. As with many other things data can tend to follow the 80/20 rule with 20% of your data accounting for 80% of the reads and often times its higher than this. Postgres itself actually tracks access patterns of your data and will on its own keep frequently accessed data in cache. Generally you want your database to have a cache hit rate of about 99%.

(Source: http://www.craigkerstiens.com/2012/10/01/understanding-postgres-performance/)

description = 'The typical rule for most applications is that only a fraction of its data is regularly accessed. As with many other things data can tend to follow the 80/20 rule with 20% of your data accounting for 80% of the reads and often times its higher than this. Postgres itself actually tracks access patterns of your data and will on its own keep frequently accessed data in cache. Generally you want your database to have a cache hit rate of about 99%.\n\n(Source: <a href="http://www.craigkerstiens.com/2012/10/01/understanding-postgres-performance/">http://www.craigkerstiens.com/2012/10/01/understanding-postgres-performance/</a>)'

get_record_item_style(record, item, index)[source]

Given a single record from MetricResult, the value of the current item within, and the current item’s index, decide how to style it. Most likely to be used with the template tag record_item_style().

By default, django-postgres-metrics supports for styling classes:

ok
warning
critical
info

Override this method and return one of the above strings or None to apply the given style to the entire record. In the Django Admin this will highlight the entire row.

header_labels = ['Reads', 'Hits', 'Ratio']: A list of strings used as column headers in the admin. Consider making the strings translateable. If the attribute is undefined, the column names returned by the database will be used.

label = 'Cache Hits': The label is what is used in the Django Admin views. Consider making this string translateable.

permission_key = 'postgres_metrics.can_view_metric_cache_hits'

permission_name = 'can_view_metric_cache_hits'

slug = 'cache-hits': A URL safe representation of the label and unique across all metrics.

sql = "\n WITH cache AS (\n SELECT\n sum(heap_blks_read) heap_read,\n sum(heap_blks_hit) heap_hit,\n sum(heap_blks_hit) + sum(heap_blks_read) heap_sum\n FROM\n pg_statio_user_tables\n ) SELECT\n heap_read,\n heap_hit,\n CASE\n WHEN heap_sum = 0 THEN 'N/A'\n ELSE (heap_hit / heap_sum)::text\n END ratio\n FROM\n cache\n {ORDER_BY}\n ;\n ": The actual SQL statement that is being used to query the database. In order to make use of the ordering, include the string {ORDER_BY} in the query as necessary. For details on that value see get_order_by_clause().

class postgres_metrics.metrics.DetailedIndexUsage(ordering=None)[source]

Bases: Metric

A metric similar to “Index Usage” but broken down by index.

The “index scan over sequential scan” column shows how frequently an index was used in comparison to the total number of sequential and index scans on the table.

Similarly, the “index scan on table” shows how often an index was used compared to the other indexes on the table.

description = 'A metric similar to "Index Usage" but broken down by index.\n\nThe "index scan over sequential scan" column shows how frequently an index was used in comparison to the total number of sequential and index scans on the table.\n\nSimilarly, the "index scan on table" shows how often an index was used compared to the other indexes on the table.'

header_labels = ['Table', 'Index', 'Index Scan over Sequential Scan', 'Index Scan on table']: A list of strings used as column headers in the admin. Consider making the strings translateable. If the attribute is undefined, the column names returned by the database will be used.

label = 'Detailed Index Usage': The label is what is used in the Django Admin views. Consider making this string translateable.

ordering = '1.2': The default ordering that should be applied to the SQL query by default. This needs to be a valid ordering string as defined on parsed_ordering.

permission_key = 'postgres_metrics.can_view_metric_detailed_index_usage'

permission_name = 'can_view_metric_detailed_index_usage'

slug = 'detailed-index-usage': A URL safe representation of the label and unique across all metrics.

sql = '\n SELECT\n t.relname,\n i.indexrelname,\n CASE t.seq_scan + t.idx_scan\n WHEN 0\n THEN round(0.0, 2)\n ELSE\n round(\n (100::float * i.idx_scan / (t.seq_scan + t.idx_scan))::numeric,\n 2::int\n )\n END,\n CASE t.idx_scan\n WHEN 0\n THEN round(0.0, 2)\n ELSE\n round((100::float * i.idx_scan / t.idx_scan)::numeric, 2::int)\n END\n FROM\n pg_stat_user_tables t\n INNER JOIN\n pg_stat_user_indexes i\n ON t.relid = i.relid\n {ORDER_BY}\n ;\n ': The actual SQL statement that is being used to query the database. In order to make use of the ordering, include the string {ORDER_BY} in the query as necessary. For details on that value see get_order_by_clause().

class postgres_metrics.metrics.IndexSize(ordering=None)[source]

Bases: Metric

description = ''

header_labels = ['Table', 'Index', 'Size']: A list of strings used as column headers in the admin. Consider making the strings translateable. If the attribute is undefined, the column names returned by the database will be used.

label = 'Index Size': The label is what is used in the Django Admin views. Consider making this string translateable.

ordering = '1.2': The default ordering that should be applied to the SQL query by default. This needs to be a valid ordering string as defined on parsed_ordering.

permission_key = 'postgres_metrics.can_view_metric_index_size'

permission_name = 'can_view_metric_index_size'

slug = 'index-size': A URL safe representation of the label and unique across all metrics.

sql = '\n SELECT\n relname,\n indexrelname,\n pg_size_pretty(index_size)\n FROM (\n SELECT\n relname,\n indexrelname,\n pg_relation_size(indexrelid) AS index_size\n FROM\n pg_stat_user_indexes\n {ORDER_BY}\n ) AS t\n ;\n ': The actual SQL statement that is being used to query the database. In order to make use of the ordering, include the string {ORDER_BY} in the query as necessary. For details on that value see get_order_by_clause().

class postgres_metrics.metrics.IndexUsage(ordering=None)[source]

Bases: Metric

While there is no perfect answer, if you’re not somewhere around 99% on any table over 10,000 rows you may want to consider adding an index. When examining where to add an index you should look at what kind of queries you’re running. Generally you’ll want to add indexes where you’re looking up by some other id or on values that you’re commonly filtering on such as created_at fields.

(Source: http://www.craigkerstiens.com/2012/10/01/understanding-postgres-performance/)

description = 'While there is no perfect answer, if you're not somewhere around 99% on any table over 10,000 rows you may want to consider adding an index. When examining where to add an index you should look at what kind of queries you're running. Generally you'll want to add indexes where you're looking up by some other id or on values that you're commonly filtering on such as created_at fields.\n\n(Source: <a href="http://www.craigkerstiens.com/2012/10/01/understanding-postgres-performance/">http://www.craigkerstiens.com/2012/10/01/understanding-postgres-performance/</a>)'

get_record_style(record)[source]

Given a single record from MetricResult, decide how to style it. Most likely to be used with the template tag record_style().

By default, django-postgres-metrics supports for styling classes:

ok
warning
critical
info

Override this method and return one of the above strings or None to apply the given style to the entire record. In the Django Admin this will highlight the entire row.

header_labels = ['Table', 'Index used (in %)', 'Num rows']: A list of strings used as column headers in the admin. Consider making the strings translateable. If the attribute is undefined, the column names returned by the database will be used.

label = 'Index Usage': The label is what is used in the Django Admin views. Consider making this string translateable.

ordering = '2': The default ordering that should be applied to the SQL query by default. This needs to be a valid ordering string as defined on parsed_ordering.

permission_key = 'postgres_metrics.can_view_metric_index_usage'

permission_name = 'can_view_metric_index_usage'

slug = 'index-usage': A URL safe representation of the label and unique across all metrics.

sql = '\n SELECT\n relname,\n round(\n (100::float * idx_scan / (seq_scan + idx_scan))::numeric,\n 2::int\n ),\n n_live_tup\n FROM\n pg_stat_user_tables\n WHERE\n seq_scan + idx_scan > 0\n {ORDER_BY}\n ;\n ': The actual SQL statement that is being used to query the database. In order to make use of the ordering, include the string {ORDER_BY} in the query as necessary. For details on that value see get_order_by_clause().

class postgres_metrics.metrics.Metric(ordering=None)[source]

Bases: object

The superclass for all Metric implementations. Inherit from this to define your own metric.

If you want to implement your own metric, here’s a gist:

from django.utils.translation import ugettext_lazy as _
from postgres_metrics.metrics import Metric, registry


class DjangoMigrationStatistics(Metric):
    """
    Count the number of applied Django migrations per app and sort by
    descending count and ascending app name.
    """
    label = _('Migration Statistics')
    slug = 'django-migration-statistics'
    ordering = '-2.1'
    sql = '''
        SELECT
            app, count(*)
        FROM
            django_migrations
        GROUP BY
            app
        {ORDER_BY}
        ;
    '''


registry.register(DjangoMigrationStatistics)

description

Don’t define this value directly. Instead define a docstring on the metric class.

The docstring will be processed by Python internals to trim leading white spaces and fix newlines. '\r\n' and '\r' line breaks will be normalized to '\n'. Two or more consecutive occurances of '\n' mark a paragraph which will be escaped and wrapped in  HTML tags. Further, each paragraph will call into Django’s urlize() method to create <a></a> HTML tags around links.

classmethod can_view(user)[source]

Check that the given a user instance has access to the metric.

This requires the user instance to have the django.contrib.auth.models.User.is_superuser and django.contrib.auth.models.User.is_staff flags as well as the django.contrib.auth.models.User.has_perm() method.

Users with is_superuser=True will always have access to a metric. Users with is_staff=True will have access if and only if the user has the permission for a metric.

full_sql: The sql formatted with get_order_by_clause().

get_data()[source]

Iterate over all configured PostgreSQL database and execute the full_sql there.

Returns:: Returns a list of MetricResult instances.
Return type:: list

get_order_by_clause()[source]

Turn an ordering string like 1.5.-3.-2.6 into the respective SQL.

SQL’s column numbering starts at 1, so do we here. Given ordering as 1.5.-3.-2.6 return a string ORDER BY 1 ASC, 5 ASC, 3 DESC, 2 DESC, 6 ASC.

Ensures that each column (excluding the - prefix) is an integer by calling int() on it.

get_record_item_style(record, item, index)[source]

Given a single record from MetricResult, the value of the current item within, and the current item’s index, decide how to style it. Most likely to be used with the template tag record_item_style().

By default, django-postgres-metrics supports for styling classes:

ok
warning
critical
info

Override this method and return one of the above strings or None to apply the given style to the entire record. In the Django Admin this will highlight the entire row.

get_record_style(record)[source]

Given a single record from MetricResult, decide how to style it. Most likely to be used with the template tag record_style().

By default, django-postgres-metrics supports for styling classes:

ok
warning
critical
info

Override this method and return one of the above strings or None to apply the given style to the entire record. In the Django Admin this will highlight the entire row.

header_labels = None: A list of strings used as column headers in the admin. Consider making the strings translateable. If the attribute is undefined, the column names returned by the database will be used.

headers: A wrapper around the header_labels to make the tables in the admin sortable.

label = '': The label is what is used in the Django Admin views. Consider making this string translateable.

max_pg_version = None

min_pg_version = None

ordering = '': The default ordering that should be applied to the SQL query by default. This needs to be a valid ordering string as defined on parsed_ordering.

parsed_ordering

Turn an ordering string like 1.5.-3.-2.6 into the respective abstraction.

Given ordering as 1.5.-3.-2.6 return a list of 2-tuples like [('', 1), ('', 5), ('-', 3), ('-', 2), ('', 6)].

slug = '': A URL safe representation of the label and unique across all metrics.

sql = '': The actual SQL statement that is being used to query the database. In order to make use of the ordering, include the string {ORDER_BY} in the query as necessary. For details on that value see get_order_by_clause().

class postgres_metrics.metrics.MetricHeader(name, index, ordering)[source]

Bases: object

A single column header; mostly takes care of a column’s sorting status.

ascending: True if the column is in ascending order False otherwise

static join_ordering(ordering)[source]

sort_priority: The priority of the columns order. 1 (high), n(low). Default 0.

url_primary: Querystring value making this the primary sorting header.

url_remove: Querystring value removing this column from sorting.

url_toggle: Querystring value toggling ascending/descending for this header.

class postgres_metrics.metrics.MetricMeta(name, bases, attrs)[source]: Bases: type

class postgres_metrics.metrics.MetricRegistry[source]

Bases: object

register(metric)[source]: Given a class (not class instance) of Metric, adds it to the available list of metrics to show it to a user.

property sorted: All registered metrics ordered by their label.

unregister(slug)[source]: Remove the metric slug from the registry. Raises a KeyError if the metric isn’t registered.

class postgres_metrics.metrics.MetricResult(connection, records)[source]

Bases: object

Hold a metric’s data for a single database.

alias: The alias under which a database connection is known to Django.

dsn: The PostgreSQL connection string per psycopg2 or psycopg.

records: The rows returned by a metric for the given database.

holds_data = True

class postgres_metrics.metrics.NoMetricResult(connection, reason)[source]

Bases: MetricResult

Internal class to pass an error message to the template when a metric is not available.

holds_data = False

class postgres_metrics.metrics.SequenceUsage(ordering=None)[source]

Bases: Metric

Show the sequence usage within a PostgreSQL database. A usage over 75% will be marked as red, and a usage over 50% will be marked as yellow.

description = 'Show the sequence usage within a PostgreSQL database. A usage over 75% will be marked as red, and a usage over 50% will be marked as yellow.'

get_record_style(record)[source]

Given a single record from MetricResult, decide how to style it. Most likely to be used with the template tag record_style().

By default, django-postgres-metrics supports for styling classes:

ok
warning
critical
info

Override this method and return one of the above strings or None to apply the given style to the entire record. In the Django Admin this will highlight the entire row.

header_labels = ['Table', 'Column', 'Sequence', 'Last value', 'Max value', 'Used (in %)']: A list of strings used as column headers in the admin. Consider making the strings translateable. If the attribute is undefined, the column names returned by the database will be used.

label = 'Sequence Usage': The label is what is used in the Django Admin views. Consider making this string translateable.

min_pg_version = 100000

ordering = '-6.1.2.3': The default ordering that should be applied to the SQL query by default. This needs to be a valid ordering string as defined on parsed_ordering.

permission_key = 'postgres_metrics.can_view_metric_sequence_usage'

permission_name = 'can_view_metric_sequence_usage'

slug = 'sequence-usage': A URL safe representation of the label and unique across all metrics.

sql = "\n SELECT\n tabcls.relname,\n attrib.attname,\n seqcls.relname,\n seq.last_value,\n seq.max_value,\n round(\n (\n 100::float * COALESCE(seq.last_value, 0)\n / (seq.max_value - seq.start_value + 1)\n )::numeric,\n 2::int\n )\n FROM\n pg_class AS seqcls\n INNER JOIN\n pg_sequences AS seq\n ON seqcls.relname = seq.sequencename\n INNER JOIN\n pg_depend AS dep\n ON seqcls.relfilenode = dep.objid\n INNER JOIN\n pg_class AS tabcls\n ON dep.refobjid = tabcls.relfilenode\n INNER JOIN\n pg_attribute AS attrib\n ON\n attrib.attnum = dep.refobjsubid\n AND attrib.attrelid = dep.refobjid\n WHERE\n seqcls.relkind = 'S'\n {ORDER_BY}\n ;\n ": The actual SQL statement that is being used to query the database. In order to make use of the ordering, include the string {ORDER_BY} in the query as necessary. For details on that value see get_order_by_clause().

class postgres_metrics.metrics.TableSize(ordering=None)[source]

Bases: Metric

The “size” of a table in PostgreSQL can be different, depending on what to include when calculating “the size”.

The “Total size” for a relation is equal to the “Table size” plus all indexes.

The “size of * fork” refers to the “main” data fork, the Free Space Map (fsm), Visibility Map (vm), and the initialization fork.

See also the PostgreSQL documentation on the physical storage: https://www.postgresql.org/docs/current/storage.html

description = 'The "size" of a table in PostgreSQL can be different, depending on what to include when calculating "the size".\n\nThe "Total size" for a relation is equal to the "Table size" plus all indexes.\n\nThe "size of * fork" refers to the "main" data fork, the Free Space Map (fsm), Visibility Map (vm), and the initialization fork.\n\nSee also the PostgreSQL documentation on the physical storage: <a href="https://www.postgresql.org/docs/current/storage.html">https://www.postgresql.org/docs/current/storage.html</a>'

header_labels = ['Table', 'Total size', 'Table size', "Size of 'main' fork", "Size of 'fsm' fork", "Size of 'vm' fork", "Size of 'init' fork"]: A list of strings used as column headers in the admin. Consider making the strings translateable. If the attribute is undefined, the column names returned by the database will be used.

label = 'Table Size': The label is what is used in the Django Admin views. Consider making this string translateable.

ordering = '1': The default ordering that should be applied to the SQL query by default. This needs to be a valid ordering string as defined on parsed_ordering.

permission_key = 'postgres_metrics.can_view_metric_table_size'

permission_name = 'can_view_metric_table_size'

slug = 'table-size': A URL safe representation of the label and unique across all metrics.

sql = "\n SELECT\n relname,\n pg_size_pretty(total_size),\n pg_size_pretty(table_size),\n pg_size_pretty(relation_size_main),\n pg_size_pretty(relation_size_fsm),\n pg_size_pretty(relation_size_vm),\n pg_size_pretty(relation_size_init)\n FROM (\n SELECT\n relname,\n pg_total_relation_size(relid) AS total_size,\n pg_table_size(relid) AS table_size,\n pg_relation_size(relid, 'main') AS relation_size_main,\n pg_relation_size(relid, 'fsm') AS relation_size_fsm,\n pg_relation_size(relid, 'vm') AS relation_size_vm,\n pg_relation_size(relid, 'init') AS relation_size_init\n FROM\n pg_stat_user_tables\n {ORDER_BY}\n ) AS t\n ;\n ": The actual SQL statement that is being used to query the database. In order to make use of the ordering, include the string {ORDER_BY} in the query as necessary. For details on that value see get_order_by_clause().