Isok -- A query centered monitoring tool for PostgreSQL
Karl O. Pinc
The Meme Factory, Inc.
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Table of Contents
Introduction to Isok
Installation
Requirements
Quick-Start
Preparing, While Logged-In to Un*x
Loading Into PostgreSQL
Uninstalling
An Overview of the Isok Tables
The Isok Main Tables
ISOK_QUERIES
ISOK_RESULTS (Isok query Results)
Isok Support Tables
IQ_TYPES (Integrity Query Types)
IR_TYPES (Isok Result Types)
The Isok Functions (Activating Isok)
run_isok_queries — execute one or more of the queries stored
in the ISOK_QUERIES table
A. Security Considerations
Limiting Access
What Queries Access Matters
The Search Path
Roles
Mitigation Strategies
Creating an Audit Trail
B. Local Copies of the Documentation
C. Periodic Execution
Example Periodic Reporting via Email Using systemd
D. Techniques For Making Local Extensions to Isok
Wrap run_isok_queries()
Extend Issue Classification
Fully Utilize ISOK_RESULTS.QR_Extra
Modify Isok's Generated SQL
E. Developing Isok
Tool Requirements
Building and Distributing
F. Acknowledgments and History
The Gombe Mother-Infant Project Acknowledgments
The Babase Acknowledgments
The SokweDB Acknowledgements
G. Isok Licensing Terms -- Licensed Under The AGPL v3.0+ (Examples
Excepted)
H. GNU Affero General Public License version 3
I. CC0 1.0 Universal Deed
No Copyright
Other Information
Notice
J. CC0 1.0 Universal
Introduction to Isok
Isok is a PostgreSQL extension for monitoring anything that can be
reported with an SQL query. Its expected usage targets data integrity
maintenance and data cleanup. One expected use-case is addressing those
corner cases where business logic is "fuzzy" and database content is
monitored for unusual but not prohibited content. There is also a
potential use-case for monitoring for errors in data, although it can be
best to use constraints and triggers for this purpose because these
prevent erroneous data from getting into the database in the first place.
Isok lets you run SQL to produce reports alerting you of suspicious or
erroneous conditions, with features to suppress previously reported
alerts. Unlike simply running a query, which reports the existence of
questionable data patterns, this method produces reports alerting you of
changes to questionable data patterns, so that only new problems need be
reviewed.
It is useful when periodically probing for unusual but allowed activity,
such as the purchase of more than 1,000 shoes by one person. Approved
excessive shoe purchases can be individually flagged so they do not appear
in future reports. To avoid being overwhelmed by numerous legitimate
alerts and to allow time to resolve issues, specific rows in the reports
can be deferred so they do not reappear before a designated date.
Unlike triggers and constraints, Isok does nothing until executed. This is
done by SELECTing FROM a function, which runs some or all of the saved
queries to check the state of the database and report the results. Report
content is archived and can be queried.
Reported issues are classified as either errors or warnings. Errors are
always reported when Isok is run. After execution, the warnings reported
by the user-supplied queries may be manually sorted by the Isok user into
one of the following categories: unclassified (the default), labeled
“resolved”, or deferred until a later date. When Isok is run, unclassified
warnings are reported, “resolved” warnings are not reported, and deferred
warnings are not reported until the current date reaches the deferral
date.
PostgreSQL supports a high degree of introspection. Isok can therefore
monitor PostgreSQL itself, both the database engine's operational metrics
and database schema design. In the former case system performance or usage
might be monitored. In the latter, monitoring might look for things like
violations of column naming conventions. However, while there may be
legitimate uses of Isok for these sorts of purposes, other tools may be a
better fit.
Regardless of how Isok is used, we believe some monitoring and some error
checking is better than no monitoring and no error checking. Isok makes
monitoring and error checking easy. If introducing triggers into your
processing or running a complete performance monitoring solution is just
not feasible, Isok provides a simple way to move the ball at least a
little bit closer to the goal.
Installation
There are two steps to installation, first, getting and preparing the code
and, when installing as an extension, installing into the OS, and, second,
loading into one or more databases.
Note
Installing Isok into the OS, which is necessary when installing as an
extension, typically requires elevated OS-level privileges, such as root
privileges. The examples given do not include the assumption of elevated
privileges, or show the use of any particulars, such as the sudo command,
needed to assume such privileges.
Similarly, the examples do not include the connection parameters
(usernames, passwords, hosts, database names, etc.) which may be needed to
connect to a database.
Regardless of how Isok is installed, we recommend you install it in a
dedicated schema. Dedicating a schema to Isok has a number of benefits,
not the least of which is simplified access control to mitigate security
concerns.^[1] When a schema is created, only the owner can access its
content. This is sufficient protection, assuming care is taken using the
ISOK_QUERIES.Role and ISOK_QUERIES.Search_Path columns. (Or, if these
features are disabled.)
Requirements
Isok installs on PostgreSQL version 10 or later, although PostgreSQL
versions no longer supported by The PostgreSQL Global Development Group
may not get support.
Quick-Start
The simplest way to get and prepare Isok is to use pgxnclient. Your
operating system probably has a pgxnclient package available.
The pgxnclient package must be installed on the machine running your
PostgreSQL server. If you're running a managed instance of PostgreSQL, in
the cloud or otherwise, and don't have access to the machine running the
PostgreSQL cluster, you'll need to use another installation method.
After installing pgxnclient, the command:
pgxn install pg_isok
makes the Isok extension available to PostgreSQL. Then, executing SQL
like:
CREATE SCHEMA isok;
CREATE EXTENSION pg_isok SCHEMA isok;
loads Isok into your database and makes it available for use.
Preparing, While Logged-In to Un*x
Installing as an extension requires that the installation be done while
logged into the PostgreSQL server's machine. Or, at minimum, while the
current working directory is within the server's filesystem.
Installing from SQL, as is necessary when the PostgreSQL's server's
filesystem is unavailable, must be done from a machine able to work as a
PostgreSQL client.
The recommended download is the Isok zip file “distribution” from
PGXN.org. It is "pre-built", and so does not require installation of any
build tooling. If you have this, after unzipping, you can skip over the
next sections, which cover disabling features, and cloud installation, and
skip straight to Installing in the PostgreSQL Server's OS.
It is also possible to clone the Isok git repository, but be forewarned.
Working from the git repository requires the installation of considerable
tooling.
Note
Any rebuild of Isok requires the installation of the m4 macro
pre-processor.^[2] Your operating system almost surely makes available an
m4 package.
Only the "pre-built" PGXN distribution can be installed without the use of
m4.
Re-Building to Disable Features
If desired, some potentially dangerous features of Isok can be disabled at
build time.
These are the make variables that control the build options:
DISABLE_ROLE
Disable the ability to SET ROLE from ISOK_QUERIES.
DISABLE_SEARCH_PATH
Disable the ability to SET the search_path.
To use these variables, set them to any value when running make. For
example, to disable all optional features run:
make DISABLE_ROLE=y DISABLE_SEARCH_PATH=y
The build configuration is documented in the
doc/pg_isok--${VERSION}.config file, and installed with the rest of the
documentation.
Building for and Installing in The Cloud (Installing With SQL)
If you are running in the cloud, or some other managed instance where you
do not have permissions on the host running PostgreSQL, you will not be
able to install Isok as an extension. In these cases you can still install
Isok, but you must first build its SQL and then manually execute it.
Of course, this installation method can always be used, as there is always
a way to execute SQL.
To build a “cloud version” of Isok, suitable for installation by SQL
execution, you would type something like:
make TARGET_SCHEMA=isok pg_isok_cloud--$(cat VERSION).sql
The resulting sql file is in the sql/ directory.
To customize the build, any of the above variables may also be set. The
TARGET_SCHEMA variable must be set; the objects produced by the generated
SQL must be located within a designated schema. It is highly recommended
that the TARGET_SCHEMA be lower-case and otherwise be a PostgreSQL name
which does not require quoting.
To install, first create the schema and then execute the sql. The command
line interaction, if you use the psql command line client interface, would
look something like:
$ psql
psql (15.13 (Debian 15.13-0+deb12u1))
Type "help" for help.
me=> CREATE SCHEMA isok; -- The TARGET_SCHEMA used to build the sql
CREATE SCHEMA
me=> \i sql/pg_isok_cloud--1.0.0.sql
<lots of output redacted>
me=> \q
$
You must re-build different SQL, with a different TARGET_SCHEMA, in order
to install into a different schema.
Installing in the PostgreSQL Server's OS
With appropriate OS-level permissions, run:
make install
With this step complete, you are ready to install the Isok extension into
any schema of any database in the cluster.
Running Regression Tests
Once an extension has been installed in the OS, regression tests can be
run to test whether Isok is operating correctly. Running the regression
tests when Isok is installed by SQL execution is unsupported.
The same build variables must be set when running the regression tests as
when the system was built. (The PGXN distribution sets no variables, the
default.) Should you set a different collection of variables than when
building, some tests will fail and others may fail to run at all.
The following example runs the default set of regression tests:
make installcheck
Loading Into PostgreSQL
The CREATE EXTENSION command is used to install Isok, as in the following
example:
CREATE SCHEMA isok;
CREATE EXTENSION pg_isok SCHEMA isok;
Uninstalling
Uninstalling From the OS
Uninstalling from the OS does the opposite of installing. It removes the
extension from the PostgreSQL server's filesystem.
To uninstall with pgxnclient, run:
pgxn uninstall pg_isok
To uninstall using make, run:
make uninstall
Because Isok is pure SQL, uninstalling it from the OS does not remove any
functionality from existing instances installed with CREATE EXTENSION.
Uninstalling does, however, remove the ability to use the CREATE EXTENSION
to install Isok in a schema.
Uninstalling From PostgreSQL
Running:
DROP EXTENSION pg_isok;
removes the extension from all schemas in all PostgreSQL clusters.
To remove an installation of Isok from an individual schema, drop the
schema with DROP SCHEMA schemaname CASCADE;.
An Overview of the Isok Tables
This section provides an overview of Isok's tables.
Table 1. The Isok Tables
+---------------------------------------------------------------+
| Table | One row for each... |
|--------------+------------------------------------------------|
| ISOK_QUERIES | query used to discover data integrity problems |
|--------------+------------------------------------------------|
| ISOK_RESULTS | data integrity problem discovered by Isok |
+---------------------------------------------------------------+
Table 2. The Isok Support Tables
+------------------------------------------------------------------------+
| Table | Id Column | Related Column(s) | One entry for every |
| | | | possible choice of... |
|----------+-----------+-----------------------+-------------------------|
| IQ_TYPES | IQType | ISOK_QUERIES.Type | kind of problem with |
| | | | data integrity |
|----------+-----------+-----------------------+-------------------------|
| | | | remark which might |
| | | | apply to more than one |
| IR_TYPES | IRType | ISOK_RESULTS.Category | instance of |
| | | | questionable database |
| | | | integrity |
+------------------------------------------------------------------------+
Figure 1. Key To Entity Relationship Diagrams
[OBJ]
Figure 2. Isok Entity Relationship Diagram
[OBJ]
The Isok Main Tables
In the table descriptions below, each table has it's own section, with
sub-sections for the table's columns.
All timestamps (date plus time values) have a one second precision.
Fractions of a second are not recorded.
All timestamps track the time zone.
ISOK_QUERIES
The ISOK_QUERIES table contains one row for every query used to search for
database integrity issues.
The Last_Run value cannot be before the First_Run value.
Tip
Use PostgreSQL's dollar quoting when inserting queries into ISOK_QUERIES
using INSERT statements. This avoids problems that would otherwise arise
involving the use of quote characters inside quoted strings.
Example 1. Inserting a query into ISOK_QUERIES using dollar quoting
-- Report a warning when there's a birth date before 1950
INSERT INTO isok_queries (iqname, error, type, keep, query, comment)
VALUES('mycheck', false, 'bdate', false
, $$SELECT 'Bad birth date: ' || mytable.id || ', ' || mytable.birthdate
AS id
, 'Id ('
|| mytable.id
|| ') has a birthdate ('
|| mytable.birthdate
|| ') before 1950'
AS msg
FROM mytable
WHERE mytable.birthdate < '1950-01-01'$$
, $$Report a warning when there's a birthdate before 1950$$
);
IQName (Isok Query Name)
A TEXT value. A unique name for the query. The IQName value cannot be
changed. This column may not be empty; it must contain characters, and it
must contain at least one non-whitespace character. This column may not be
NULL. This column may not contain whitespace characters. This column must
be unique when compared in a case-insensitive fashion.
Error
A BOOLEAN value. TRUE when the query finds conditions that are errors,
FALSE when the query finds conditions that are warnings. See ISOK_RESULTS
(and the Introduction to Isok) for more on warnings and errors.
This column may not be NULL.
Type
A TEXT value. Code classifying the query. The legal values for this column
are defined by the IQ_TYPES support table.
This column may not be NULL.
First_Run
A timestamp. Date and time the query was first run by Isok. The value of
this column is NULL if the query has never been run.
Last_Run
A timestamp. Date and time the query was most recently run by Isok. The
value of this column is NULL if the query has never been run.
Keep (Keep old results)
A BOOLEAN value. This column controls the value placed in the
ISOK_RESULTS.Keep_Until column when run_isok_queries() inserts new rows in
ISOK_RESULTS.
When this column is TRUE, each row returned by the query is stored in
ISOK_RESULTS with a Keep_Until value of infinity. This prevents
run_isok_queries() from deleting the query result row when run, when the
query no longer returns the result row.
When this column is FALSE, the ISOK_RESULTS.Keep_Until value of any new
rows that run_isok_queries() inserts is NULL.
This column may not be NULL.
Role
A PostgreSQL name value. The PostgreSQL role to use to run the query.
Because different roles have differing access to database content, it can
be useful to run queries with different roles in effect.
Caution
Setting the role may have security implications.
This column is not validated against existing roles.
Note that the name data type casts (transparently) to TEXT.
When this column is NULL, the effective role is not changed.
Search_Path
A TEXT value. The PostgreSQL schema search_path to have in effect when the
query is run.
The syntax of the search path is that used by SET search_path ... and
returned by SHOW search_path;.
Because queries may not always contain schema names to qualify database
objects, a single query can return different results depending on the
search_path in effect. So it can be useful to run different queries when
different schema search paths are in effect.
Caution
Setting the search_path may have security implications.
Care must be taken when setting the search path because the search path
can be set to anything, regardless of which schemas exist or are available
to the user. It is quite easy to set a search path that searches no
schemas. PostgreSQL will not produce any warnings or errors should you do
so.
When this column is NULL, the schema search path is not changed.
Query
A TEXT value. A query which checks for database integrity violations. The
query need not end in a semi-colon. The query must return 3 columns.
Although these columns are referred to by name below, the names the query
gives to the columns does not matter.
The first returned column, the ID column
The first column is used as an id. It must contain a unique value. (Unique
per results returned by the given query). The value must also be constant;
repeated runs of the query which find the same problem must return a
consistent value.
Caution
The system cannot enforce the requirement that the first column be
consistent over repeated runs of the query. If the query does not satisfy
this requirement Isok will generate duplicates of previously reported
problems.
The value of the first column may not be NULL or the empty string.
Guidelines for the value of the first column are that it should be human
readable and relatively short. It should probably contain id values in
order to ensure uniqueness, but only those that will not change over time.
The value of this first column may need to be typed in or otherwise
referenced by a person in order to make notes regarding the problem or to
change the problem's status.
The second returned column, the Msg column
The second column contains a message describing the discovered database
integrity problem. It should contain a complete description of the problem
and may be as verbose as necessary.
The value of the second column may not be NULL or the empty string.
The third returned column, the Extra JSON column
The third column contains JSON data. The purpose of this column is to hold
additional data on the reported condition that may need to be tracked, or
queried. PostgreSQL is able to efficiently query JSONB data, which is how
this column is stored.
Warning
At the time of this writing, in practice, returning a third column is
optional. But this behavior should not be relied upon.
Best practice is to return a NULL value for the third column when you do
not wish to store any JSON with the query result.
When only 2 columns are returned, the effect is the same as returning a
NULL value in the third column.
The third column is optional, in practice, because a portion of of the
PostgreSQL PL/pgSQL language is unspecified.^[3]Isok cannot feasibly use
the text of the Query column to determine how many columns the query
returns. So it cannot prevent the query from being written to return only
two columns. And, when this is the case, the present PL/pgSQL
implementation allows the Query to return two columns instead of three.
Return a NULL value in the third column when there is no JSON data.
Comment
A TEXT value. A comment on the query. This may be as verbose as necessary.
This column may not be NULL. This column may be empty; it need not contain
characters, but it may not contain only whitespace characters..
ISOK_RESULTS (Isok query Results)
The ISOK_RESULTS table contains one row for every database integrity
problem discovered by the queries in ISOK_QUERIES. That is to say, one row
for every row returned by executed queries. The table's purpose is
twofold. It provides an efficient way to list data integrity problems,
without having to execute the potentially complex queries which discover
the problems. But it's main purpose is to allow warnings, i.e. those
problems discovered by the queries saved in ISOK_QUERIES rows having a
FALSE Error value, to be resolved -- permanently marked as acceptable
conditions. Resolved warnings can be safely ignored thereafter, and since
Isok automatically ignores resolved warnings those responsible for
maintaining database integrity need not repeatedly concern themselves with
resolved conditions.
To resolve a warning place a timestamp in the Resolved column.
Data integrity errors can not be resolved, the erroneous data condition
must be fixed -- ISOK_RESULTS rows must have a NULL Resolved value when
the row has a IQName related to an ISOK_QUERIES row having a TRUE Error
value.
The Last_Seen value, the Resolved value, and the Deferred_To value cannot
be before the First_Seen value.
A resolved warning cannot be deferred -- either Resolved or Deferred_To,
or both, must be NULL.^[4]
The query result id generated by the stored query must be unique per query
-- the combination of ISOK_RESULTS.IQName and ISOK_RESULTS.QR_ID must be
unique.
IRID (Integrity Results Identifier)
An BIGINT value This column uniquely identifies the row containing the
result of a database integrity query. The IRID value cannot be changed and
is automatically generated with a PostgreSQL sequence.
IQName (Integrity Query Name)
A TEXT value. The ISOK_QUERIES.IQName value identifying the query which
produced the result.
First_Seen
A timestamp value. Date and time the query result was first produced by
Isok. This column may not be NULL.
Last_Seen
A timestamp value. Date and time the query result was most recently
produced by Isok. This column may not be NULL.
Last_Role
A PostgreSQL name value. The role (user) which was the current role when
the query was last executed. Note that the name data type casts
(transparently) to TEXT.
This column is not validated against existing roles.
This column may not be NULL.
Last_Schemas
An array of PostgreSQL name values. All schemas that were, implicitly or
not, in the search_path, and also available to the Last_Role, when the
result was returned. For more information, see the documentation of the
current_schemas() function.
Note that the name data type casts (transparently) to TEXT. This column
may not be NULL.
Resolved (Date and Time Resolved)
A timestamp value. Date and time the query result was resolved; that is,
marked not a concern. The Isok system does not display resolved results,
although of course the ISOK_RESULTS table can always be manually queried.
The value of this column may be NULL. This occurs both when the query
result is a data integrity error and when it is a data integrity warning
that has not yet been resolved.
Deferred_To
A timestamp value. Isok suppresses display of the result when the current
time is before this time. Use of this column allows resolution of data
integrity problems to be deferred, and hence not clutter up the output of
Isok with noise that might hide other problems.
When this column is NULL Isok displays the query result.
Category
A TEXT value. Code classifying the query result. The legal values for this
column are defined by the IR_TYPES support table.
This column may be NULL when the query result is unclassified.
Keep_Until
A timestamp value. This column controls whether or not run_isok_queries()
deletes the row when the ISOK_QUERIES.Query is re-run and the query does
not return the row's QR_ID.
A query result that the query no longer returns is kept until the given
time is reached, when the value of this column is not NULL. When the value
of this column is NULL, a query result row that is no longer returned is
is always deleted. For further detail see the Deletion of Old Results
section of the run_isok_queries() documentation.
Tip
Using the special TIMESTAMP value of infinity entirely prevents deletion.
QR_ID (Query Result IDentifier)
A TEXT value. This is a unique, unique per query that is, identifier for
the query result. It is the first column produced by the related
ISOK_QUERIES.Query.
This column may not be NULL.
QR_Message (Query Result Message)
A TEXT value. This is the message, the second column, produced by the most
recent execution of the ISOK_QUERIES.Query.
QR_Extra (Query Result Extra JSON data)
A JSONB value. The value of the third, optional, column returned by most
recent execution of the query. This may contain any JSON deemed useful.
This column serves as a catch-all container for any additional data that
needs to be tracked regarding a reported condition.
The value of this column may be NULL. This is the default when the
ISOK_QUERIES.Query does not return a third column.
See PostgreSQL's documentation on the JSON data types for information on
how to access, index, and efficiently query the JSONB data type.
Notes
A TEXT value. Any notes regarding this particular query result. This
column may not be NULL. This column may be empty; it need not contain
characters, but it may not contain only whitespace characters.
Isok Support Tables
Support tables are used to control the values used in other tables. Each
support table has a key, with an appropriate column name, and a column
named Description. Both of these columns are of type TEXT. The keys of the
support table are foreign keys of a column which has a controlled
vocabulary, a limited number of terms which are allowed to be used.
An administrator can add or remove rows from the support tables to
dynamically control the allowed vocabulary.
The support table Description columns must be unique when the comparison
is made in a case-insensitive manner.
IQ_TYPES (Integrity Query Types)
IQ_TYPES contains one row for every code used to classify database
integrity queries. Classification may be by the type of data integrity
problem the related queries are designed to uncover, by who is responsible
for resolving the discovered problems, or any other desired classification
scheme.
Key: IQType
The IQ_TYPES table is keyed by the IQType column. This column may not
contain whitespace characters. This column must be unique when compared in
a case-insensitive fashion.
IR_TYPES (Isok Result Types)
IR_TYPES contains one row for every code used to classify or explain sets
of database integrity problems, problems discovered by Isok's queries.
Codes may be used as needed, whether to organize reported problems pending
resolution, to describe the circumstances which resolve an issue, or to
serve other purposes.
Key: IRType
The IR_TYPES table is keyed by the IRType column. This column may not
contain whitespace characters. This column must be unique when compared in
a case-insensitive fashion.
The Isok Functions (Activating Isok)
Isok is run by using one of its functions. Of course the ISOK_RESULTS
table may always be queried manually, but this does not discover any new
problems.
All of the Isok functions are designed to be used in the FROM clause of
SELECT statements, as if they were tables. Indeed the functions look like
tables to the SELECT statement, tables that look exactly like ISOK_RESULTS
-- except that the Resolved column is missing. The difference between
querying on the ISOK_RESULTS table directly and querying using Isok's
functions is that the functions update the content of the ISOK_RESULTS
table by executing the the queries in ISOK_QUERIES table. Also, the
functions never return rows where the underlying ISOK_RESULTS row has a
non-NULL Resolved value or a Deferred_To time and date that has not yet
been reached.
All timestamps, date plus time values, which Isok updates in the
ISOK_QUERIES and ISOK_RESULTS tables are set to the date and time at which
program execution started. So when, say, run_isok_queries(), is run, all
of the new timestamp values in the ISOK_QUERIES and ISOK_RESULTS rows
touched by the execution are identical.
Various Isok functions (or versions of the same function) are supplied to
allow easy selection of which queries in which ISOK_QUERIES rows are to be
executed, whether all or only some.
Note
As with a regular table, the order in which rows are returned by Isok's
functions is unspecified. If you wish to ensure a specific ordering an
ORDER BY clause must be used.
Name
run_isok_queries — execute one or more of the queries stored in the
ISOK_QUERIES table
Synopsis
TABLE (irid, iqname, first_seen, last_seen, category, qr_id, );
qr_message, notes) run_isok_queries (
TABLE (irid, iqname, first_seen, last_seen, category, iqname_query);
qr_id, qr_message, notes) run_isok_queries (
TEXT iqname_query ;
Input
iqname_query
The text of an SQL query. The query must return a single column of
ISOK_QUERIES.IQName values.
Description
A function which runs the queries stored in the ISOK_QUERIES table,
returns the output of the stored queries, and stores the results in the
ISOK_RESULTS table. Because the function returns rows and columns it must
be invoked in the FROM clause of a SELECT statement. (See the Examples
below.)
The function may be called in one of two ways. When called with no
arguments all of the queries in ISOK_QUERIES are run. When called with the
text of an SQL query, a query which returns a single column containing
ISOK_QUERIES.IQName values, the function runs only those queries.
Tip
Use PostgreSQL's dollar quoting when supplying a query to
run_isok_queries().
The function returns a set of columns with multiple rows, a table. So it
is expected to be used in the FROM clause of a SELECT statement. The
columns returned by the function are the columns of the ISOK_RESULTS
table, excepting the Resolved column.
The rows returned by the function are those of the newly updated
ISOK_RESULTS table, excepting those rows with a non-NULL Resolved column
or those rows with a Deferred_To value that is in the future. Only those
rows that are related to the executed queries (in ISOK_QUERIES) are
returned. So, when called with no arguments the function returns all
warnings that have not been resolved and all errors. When called with a
query that selects specific ISOK_QUERIES to execute, only the unresolved
warnings and errors discovered by the executed ISOK_QUERIES are returned.
The Record of Query Execution
Running an ISOK_QUERIES.Query does more than add new rows to the
ISOK_RESULTS table. Updates are made to existing rows to record and track
the query execution's results.
The ISOK_QUERIES.Last_Run value is updated.
On ISOK_RESULTS, the rows to update are found by matching the
ISOK_RESULTS.IQName value with the ISOK_QUERIES.IQName of the executed
query, while also matching the QR_ID value with the value returned in the
first column of the executed query. The columns updated are: Last_Seen ,
Last_Role , Last_Schemas , QR_Message , and QR_Extra.
Because the record of the results produced by Isok queries are updated, a
query may be refined over time to produce enough information to resolve
the reported issues.
Even though the execution of run_isok_queries() does not return rows that
are resolved, all rows returned by an executed query have all the
aforementioned columns updated to new values. Whether a row is returned or
not does not matter, the update occurs anyway.
Deletion of Old Results
If an existing ISOK_RESULTS row matches the IQName value of the executed
query and there is no corresponding QR_ID value returned by the executed
query, and the value of ISOK_RESULTS.Keep_Until is either NULL or
CURRENT_TIMESTAMP^[5] is not earlier than ISOK_RESULTS.Keep_Until then the
ISOK_RESULTS row is deleted. This empties the ISOK_RESULTS table of errors
and warnings that no longer apply to the current state of the database.
If the query returns warnings, this deletion behavior does not depend upon
whether or not the warning is resolved.
Examples
The following example runs all the queries in ISOK_QUERIES, displays all
the errors and all the unresolved warnings (unless the error or warning
has been deferred), ordered first by the name of the query, within that
showing newer problems first, and within that ordered by warning id.
Example 2. Executing all ISOK_QUERIES
SELECT *
FROM run_isok_queries() AS problems
ORDER BY problems.iqname
, problems.first_seen DESC
, problems.qr_id;
The following example runs a single saved query with an
ISOK_QUERIES.IQName of mycheck and displays any of these sorts of problems
found, ordered as in the previous example. This example also demonstrates
how to use dollar quoting to give a query to run_isok_queries and thereby
avoid problems having to do with trying to nest regular quotes.
Example 3. Executing a single ISOK_QUERIES.Query
SELECT *
FROM run_isok_queries($$SELECT 'mycheck'$$) AS problems
ORDER BY problems.iqname
, problems.first_seen DESC
, problems.qr_id;
The following example runs multiple specific queries, those with an
ISOK_QUERIES.IQName of mycheck, yourcheck, and theircheck, and displays
any of these sorts of problems found, ordered as in the previous example.
As before, dollar quoting is used to quote the query which produces the
IQNames.
Example 4. Executing many specific ISOK_QUERIES.Query-s
SELECT *
FROM run_isok_queries($$VALUES ('mycheck')
, ('yourcheck')
, ('theircheck')$$) AS problems
ORDER BY problems.iqname
, problems.first_seen DESC
, problems.qr_id;
The following example runs all the queries of the bdate type and displays
any of these sorts of problems found, ordered as in the previous example.
Again, dollar quoting is used.
Example 5. Executing ISOK_QUERIES of the “bdate” type
SELECT *
FROM run_isok_queries(
$$SELECT isok_queries.iqname
FROM isok_queries
WHERE isok_queries.type = 'bdate'$$
) AS problems
ORDER BY problems.iqname
, problems.first_seen DESC
, problems.qr_id;
----------------------------------------------------------------------
^[5] The time the current transaction started, which, if a transaction was
not explicitly started, is the time the database engine received the
current SQL statement from the client and began execution.
A. Security Considerations
The security concerns surrounding Isok are many, and can be complex.
Fundamentally, this is because Isok executes arbitrary SQL. If the wrong
SQL is executed, in the wrong context, anything might happen to your data.
This appendix identifies pertinent issues, and how to minimize risk.
Ultimately, these are the same issues that arise in any application that
executes SQL. The big difference between Isok and other applications is
that most applications execute a more-or-less limited number of SQL
queries that are carefully crafted to suit a specific purpose. The queries
executed by Isok can have much more variation, and be subject to less
review.
In the end, the recommendations here come down to following generally
accepted security best-practices, in particular, the principle of least
privilege.
Limiting Access
Limiting access to Isok is a clear first-step. Installing Isok into a
dedicated schema goes a long way toward helping with this. When a schema
is created, only the owner has access.^[6]So, unless GRANTs are issued,
access is limited by default.
Remember also, the ISOK_RESULTS table contains query output that may
contain sensitive information to which access should be restricted. And,
even if this is not true today, it may become true when additional queries
are added to ISOK_QUERIES.
Even the queries in ISOK_QUERIES could, possibly, contain sensitive
information.
What Queries Access Matters
The executed queries, the ISOK_QUERIES.Querys, can be any SQL statement.
Obviously, what executes matters. Less obviously, the ownership of and
permissions granted on every object referenced by every query also
matters.
Really, when multiple schemas are in the search_path, it is the ownership
of and permissions granted on every object that might be referenced by
every query that matters.
The ownership and permissions of referenced objects matter because these
factors ultimately control what any given query actually does. If a user
has, for example, permission to alter a view with some given name, or
replace a table having that name with a view that has the same name, then
the user can change what happens when that name is used in a query. The
user can write a view that does anything. Or at least anything that the
role which runs run_isok_queries() is allowed to do.
Imagine, the new view could call a function, say, in place of a table that
was referenced, and that function could do anything at all. Even while
still returning the replaced table's rows, so as to produce a results
identical to that produced before the system was altered.
That is the issue. The user executing the saved query is dependent upon
the goodwill of all the users who have enough access to alter any of the
objects involved when the query is executed.
The Search Path
The ISOK_QUERIES.Search_Path column allows setting of the search_path on a
per-query basis. The security implications of changing the search_path may
be the hardest to reason through. The crux of the problem is that
different users may have different permissions on the search path's
schemas, and on the objects the schemas contain. This opens up the
possibility that a malicious user may create an object, say, a view or a
function, in a schema which appears earlier in the search path than the
schema holding the object the query expects to find. If this is the case,
the query will use the malicious object instead of the expected object.
The PostgreSQL documentation contains an analysis of this situation, in
the context of writing SECURITY DEFINER functions. However, the analysis
in the PostgreSQL documentation is not entirely applicable to Isok. In the
case of Isok, even when Isok changes the effective role, the position in
the search path of the temporary table schema, pg_temp, is less relevant.
Because temporary tables are not shared between connections, the creation
of a malicious object in the temporary schema must be done in the current
connection. And so the issue is no different from that which occurs when
any other malicious object is created in the current connection. In either
case, there is a security lapse that occurs dynamically, at some point in
the current connection.
Having said that, moving pg_temp to the end of the search path does make
it harder to “mask” an existing object with a malicious object. Because
all roles have permission to create objects in pg_temp, a malicious actor
would not be able to mask an existing object with an object in pg_temp if
pg_temp is at the end of the search path. For this reason it may make
sense to always put pg_temp at the end of the search path whenever Isok is
used.
The PostgreSQL documentation's observation remains valid: Malicious users
with the ability to change objects in the search path may inject malicious
objects.
Roles
The role in effect does have security implications. But changing a role
for the duration of a query's execution, with ISOK_QUERIES.Role, has fewer
security implications than it might seem.
Changing the current role does open up the possibility that database
objects to which the new role has access may be changed. But this door is
already open. A new role cannot be assumed without some chain of SET
option grants from the session_user [definition here(-ish)] to the current
role. So a malicious actor always has access to the same set of roles,
regardless of whether Isok is involved or not.
What might be surprising is that, even though a role may SET ROLE to
another, perhaps with less privileges, it is always possible to use RESET
ROLE (or SET ROLE NONE) and reset the current role to the session_role.
There is no sandboxing. If the session sets a role before running
run_isok_queries(), there is the possibility that a malicious actor might
undo the assumption of the role. This could then affect the role used to
execute any queries that run_isok_queries() has not yet executed.
Don't expect that a SET ROLE to a role of lesser privileges makes running
run_isok_queries() any safer.
Mitigation Strategies
There is no one-size-fits-all solution. Even disabling Isok's ability to
dynamically alter the current search path and the current role does not
address the fundamental issues. Even more so because, to be useful,
run_isok_queries() may need an expansive set of permissions to do its job.
One possible strategy is to always supply values in the ISOK_QUERIES.Role
ISOK_QUERIES.Search_Path columns. At least that way the context of each
query's execution is always known.
Another possible strategy is to install Isok in multiple schemas, each
schema dedicated to a different purpose and assigned different
permissions, intended to be used by different users.
Creating an Audit Trail
To better respond to a suspected security problem it is always very useful
to have an audit trail to examine. One way to have such a trail is to
install a temporal extension. These extensions track the history of
database content over time. The Isok tables could be temporally tracked,
to audit what queries were changed when, as well as what query results
were produced or deleted when.
A conceivable, although entirely untested on our part, idea is to use a
temporal extension to track changes made to the postgres database.
Otherwise known as the system catalog, pg_catalog, this database contains
the definitions of all objects in all databases. Tracking the catalog
provides an audit trail should a malicious object be created, although
this would not help if pg_temp was involved.
Some installations may even want to temporally track all their tables,
although this may not be feasible for a whole host of reasons.
B. Local Copies of the Documentation
When Isok is installed as an extension, local copies of the documentation
are installed. The pg_config PostgreSQL client command provides an easy
way to find the documentation.
Example B.1. Finding the Documentation of Locally Installed Extensions
$ printf '\nExtension documentation is located in:\n%s\n\n' $(pg_config --docdir)/extension/
Extension documentation is located in:
/usr/share/doc/postgresql-doc-15/extension/
$ ls $(pg_config --docdir)/extension
pg_isok--1.0.0.config pg_isok_html pg_isok_usletter.pdf
pg_isok_a4.pdf pg_isok.txt
$ printf '\nThe URL used to read the local HTML documentation is:\nfile://%s\n\n' \
$(pg_config --docdir)/extension/pg_isok_html/html_paginated/index.html
The URL used to read the local HTML documentation is:
file:///usr/share/doc/postgresql-doc-15/extension/pg_isok_html/html_paginated/index.html
C. Periodic Execution
A monitoring system must periodically execute and deliver reports if it is
to monitor and provide actionable alerts on an ongoing basis. Isok does
not include a periodic job scheduler. Tools like the Unix cron command,
the systemd timer system, or the PostgreSQL pg_cron extension are useful
to automate, and make periodic, Isok's monitoring. There are plenty of job
schedulers available and one of these must be used to schedule the
production of Isok's reports.
Typically, something must deliver the reports Isok produces, because
push-notifications remind people to act. Although Isok does archive the
reports it produces, it does not include a report delivery mechanism.
Email, or other push-based delivery mechanisms (perhaps email-to-SMS text
gateways), are the expected delivery mechanisms for Isok's reports. Isok
itself can report to standard out when run from psql. Depending on your
job scheduler, some amount of scripting may be required to route Isok's
reports to a push delivery service.
Example Periodic Reporting via Email Using systemd
The files shown below deliver an Isok report, if there is something to
report, by email every Tuesday morning.
The system on which they are installed must have a mail transfer agent
installed, like Postfix, to begin the email delivery process. The system
also must have GNU mailutils installed, or an equivalent mail command,
like BSD mailx, to send the email.
Most operating systems will have packages available to install these
services, and a way to configure simple defaults. However, it is
non-trivial to reliably deliver email from your system directly to the
rest of the Internet. The recommended approach is to send the email from
your local system to a mail relay provided by your local IT professionals.
(Or, your Internet Service Provider. Or, if you are hosted in the cloud,
contact your hosting company.) These professionals will usually be able to
supply you with what you need to know to have mail sent from your system
to a system able to send email to the Internet at-large. If not, there are
companies that provide this service for a nominal fee.
The service you would ask for is usually called an email relay service.
It is usually a good idea to ask your local IT professionals to help with
the selection of a mail transfer agent.
This example is expected to run, as is, on most systems that have the
default PostgreSQL install.
The example assumes that pg_hba.conf contains:
local all postgres peer
This line is typically present, but this is not guaranteed.
Example C.1. Sample /usr/local/bin/pg_isok_report File
#!/usr/bin/bash
#
# Run pg_isok, and mail (with GNU mailutils) if it produces anything.
#
# Expected enviornment variables:
# CONNECTION_STRING
# The postgres connection string (or other arguments)
# Putting passwords in here is a bad idea, change pg_hba.conf instead?
# ISOK_SCHEMA
# The schema in which pg_isok is installed
# The recommendation is to _not_ change this. Instead, make an
# alias for "pg_isok_report" in /etc/aliases.
MAIL_RECIPIENT=pg_isok_report
EMPTY_FILE=$(/usr/bin/mktemp --tmpdir pg_isok_empty.XXXXXXXXXX)
OUTPUT=$(/usr/bin/mktemp --tmpdir pg_isok_output.XXXXXXXXXX)
PSQL="/usr/bin/psql ${CONNECTION_STRING}"
cleanup () {
/usr/bin/rm -rf ${EMPTY_FILE} ${OUTPUT}
}
trap cleanup EXIT
PAGER= ${PSQL} --command="
SELECT irid, iqname, first_seen, last_seen, last_role
, last_schemas, deferred_to, category, keep_until
, qr_id, qr_message, qr_extra, notes
FROM ${ISOK_SCHEMA}.isok_results
LIMIT 0;
" \
> ${EMPTY_FILE} 2>&1
PAGER= ${PSQL} --command="SELECT * FROM ${ISOK_SCHEMA}.run_isok_queries();" \
> ${OUTPUT} 2>&1
cmp --quiet ${EMPTY_FILE} ${OUTPUT} \
|| { /usr/bin/mail -s 'Isok output' ${MAIL_RECIPIENT} \
< ${OUTPUT} ; }
Example C.2. Sample /etc/systemd/system/isok_report.timer File
[Unit]
Description=Tuesday report from pg_isok
[Timer]
# See: man 7 systemd.time
OnCalendar=tuesday *-*-* 3:00
RandomizedDelaySec=60m
Persistent=true
[Install]
WantedBy=timers.target
Example C.3. Sample /etc/systemd/system/isok_report.service File
[Unit]
Description=Run pg_isok's run_isok_queries() function and email when there's\
a result
ConditionACPower=true
[Service]
#
# Configuration is done here (and in /etc/aliases, see pg_isok_report)
#
# The postgres connection string (or other arguments to psql)
# Putting passwords in here is a bad idea, change pg_hba.conf instead?
Environment="CONNECTION_STRING=mydatabase"
# Put a connection string variable assignment containing secrets in this file:
# (man 5 systemd.exec)
#EnvironmentFile=/etc/pg_isok_secrets
# The schema in which pg_isok is installed
Environment="ISOK_SCHEMA=isok"
# End of configuration
# The Uni*x user running the db engine
# (Expected to be the same as the PostgreSQL bootstrap superuser)
User=postgres
Type=oneshot
KillMode=process
PassEnvironment=CONNECTION_STRING ISOK_SCHEMA
ExecStart=/usr/local/bin/pg_isok_report
After installation, don't forget to run:
systemctl daemon-reload
systemctl enable pg_isok_report.timer
systemctl start pg_isok_report.timer
D. Techniques For Making Local Extensions to Isok
Should you find yourself wishing that Isok did more, here are some
suggested techniques for extending the functionality of your Isok
instance. There is overlap, more than one technique may facilitate
reaching any given goal.
Wrap run_isok_queries()
To perform actions before or after execution of run_isok_queries(), write
a new function that takes run_isok_queries()'s arguments and returns
run_isok_queries()'s results. And does what you wish before or afterward.
So, for example, to ensure a safe, consistent, value for search_path, you
could write a function that executes SET search_path ...;, before itself
calling run_isok_queries() and returning the result.
Extend Issue Classification
If you would like additional ways to classify the issues your queries
discover, the IR_TYPES table may be extended.
Create your own table to do this, called, say, IR_TYPE_CLASSES.
The key of this table is that of the IR_TYPES table; may as well call it
IRType. It is a foreign key, referencing IR_TYPES. So your new table has a
one-to-one relationship with IR_TYPES.
Add as many columns as you like to your new table, a column for each
(orthogonal) sub-category by which you would like to classify reported
issues. Boolean columns behave as a tag, toggling classification. Other
kinds of columns, possibly containing foreign keys to control the
vocabulary used, allow richer classification schemes.
Fully Utilize ISOK_RESULTS.QR_Extra
Indexing the JSONB ISOK_RESULTS.QR_Extra column improves performance.
If you know your JSONB keys, you can make a VIEW that exposes the value of
those keys as the view's columns. Users of this view would not have to be
familiar with querying JSONB.
More complex schemes involve putting a row-level BEFORE trigger on
ISOK_RESULTS to distribute the various values appearing in ISOK_RESULTS
into other tables. But doing so surely takes you past the point of
diminishing returns. It is easier to modify the SQL that Isok installs.
And doing so is probably also less of a long-term maintenance burden,
which matters.
Modify Isok's Generated SQL
Should you want to make a modification like allowing the queries in
ISOK_QUERIES.Query to return additional columns, you can do so by
modifying the SQL that Isok loads.
Isok is pure SQL, so the SQL can be generated and then modified, in any
way you like, before being loaded into a database's schema.
E. Developing Isok
We consider Isok to be feature complete. That said, there's always room
for improvement and contributions are welcome. Never the less, if you
would like your changes added to Isok, before doing a lot of work we
recommend communicating with us.
You are, of course, free to make changes to your local Isok.
Development should be done by cloning the git repository.
Tool Requirements
Isok uses the PGXN.org tools for building and distribution, which in turn
uses parts of the PostgreSQL GNU make-based build system. So GNU make is
required. In addition, the Isok documentation is done with the DocBook, as
is PostgreSQL's, so the tooling required to build the documentation is the
same as PostgreSQL, although Isok currently generates XHTML so may require
a slightly different set of DTDs.
Aside from these requirements, the following additional tools are needed:
DBLatex
The DocBook to LaTeX to PDF, etc., converter
gawk
The GNU awk implementation
Gnu m4
The macro pre-processor used by GNU autoconf, etc.
links
The command-line web browser
xmllint
The XML linter
zip
The archive and compression tool
DBLatex also requires the installation of various TeX and LaTeX tooling,
which your O/S's package manager is likely to install as a dependency.
When working with DocBook, the book DocBook XSL: The Complete Guide from
Sagehill.net may also be useful.
Building and Distributing
Run make help for help on the Makefile targets.
Almost all the generated files are included in the distribution. This is
so that the user, or the PGXN tooling, can use the Makefile for
installation, and uninstallation, without having to have all the tooling
required for development installed.
F. Acknowledgments and History
Isok was first developed as "The Warning System" for the Gombe Mother
Infant Database Project. It was later incorporated into Babase, part of
The Amboseli Baboon Research Project, and enhanced to take advantage of
the features in PostgreSQL 9.1. Further enhancement, including release as
a PostgreSQL extension, was done for The SokweDB Project, developed by The
Jane Goodall Institute.
We would like to thank these projects, and their funding sources, for
enabling the development and release of Isok.
The acknowledgments included in the above projects' documentation are
reproduced below. (Verbatim, excepting some updated contact information.)
It is not clear how applicable the entirety of the acknowledgments are,
but we would rather be overly generous in our thanks than be stingy.
The following acknowledgments do not include all the people who have
enabled and assisted Isok development. You know who you are. Thank you.
And thanks to the larger Open Source community. Without their support, and
hard work, none of this would have happened.
The Gombe Mother-Infant Project Acknowledgments
The Gombe-MI Development Group
Karl O. Pinc
Book Author, System Design Lead, Implementation
Carson M. Murray, PhD..
Project Co-Leader, System Design Core Member
Elizabeth V. Lonsdorf, PhD..
Project Co-Leader, System Design Core Member
Karen Anderson
System Design Core Member, Copy Review, System Testing Lead
A. Catherine Markham, PhD..
System Design Participant
Margaret A. Stanton, PhD..
System Design Participant, System Testing Core Member
Edward Wilkerson, Jr..
System Design Participant
Funding and Support. We gratefully acknowledge the support of The National
Institutes of Health grant R00HD057992 for the development of this system.
We are also very grateful for the support given by The Leo S. Guthman
Foundation, the Lincoln Park Zoo, Franklin & Marshall College, and The
George Washington University.
Other Thanks. We would like to thank the myriad Free and Open Source
communities, including those of PostgreSQL, the GNU Project, the Debian
Project, Ubuntu, PhpPgAdmin, the Pyramid web framework, TeX and LaTeX,
DBLatex, DocBook, Babase, and many others unmentioned, for giving, gratis,
billions of dollars^[7] of work to the world, without which the Gombe-MI
software and this book would not exist.
Any opinions, findings, conclusions or recommendations expressed in this
material are those of the author(s) and do not necessarily reflect the
views of the National Institutes of Health, The Leo S. Guthman Foundation,
the Lincoln Park Zoo, Franklin & Marshall College, The George Washington
University, or any other organization which has supplied support for this
work.
The Babase Acknowledgments
We gratefully acknowledge the support of the National Science Foundation
for the supporting the collection of the majority of the data stored in
the database; in the past decade in particular we acknowledge support from
IBN 9985910, IBN 0322613, IBN 0322781, BCS 0323553, BCS 0323596, DEB
0846286, DEB 0846532 and DEB 0919200. We are also very grateful for
support from the National Institute of Aging (R01AG034513-01 and
P01AG031719) and the Princeton Center for the Demography of Aging
(P30AG024361). We also thank the Chicago Zoological Society, the Max
Planck Institute for Demographic Research, the L.S.B. Leakey Foundation
and the National Geographic Society for support at various times over the
years. In addition, we thank the National Institute of Aging
(R03-AG045459-01) for supporting recent work extending the database to
incorporate genetic and genomic data.
Any opinions, findings, conclusions or recommendations expressed in this
material are those of the author(s) and do not necessarily reflect the
views of the National Science Foundation, the National Institute of Aging,
the Princeton Center for the Demography of Aging, the Chicago Zoological
Society, the Max Planck Institute for Demographic Research, the L.S.B.
Leakey Foundation, the National Geographic Society, or any other
organization which has supplied support for this work.
The SokweDB Acknowledgements
At the time of this writing, there is no formal set of acknowledgments for
SokweDB.
However, Microsoft provided funding for SokweDB and we would like to
acknowledge and thank them for their support.
Any opinions, findings, conclusions or recommendations expressed in this
material are those of the author(s) and do not necessarily reflect the
views of Microsoft.
G. Isok Licensing Terms -- Licensed Under The AGPL v3.0+ (Examples Excepted)
Isok, otherwise known as pg_isok, is licensed under the GNU Affero General
Public License version 3 (AGPL 3.0+), or (at your option) any later
version, with the exception of all sample program code, sample commands,
and sample configuration file components contained in the documentation,
whether explicitly labeled as an example or not. These samples of program
code, commands, and configuration file components are licensed under the
CC0 1.0 Universal license.
The deed for the CC0 1.0 Universal license explains the license in plain
language. The deed is reproduced in Appendix I. The No Copyright section
captures the essence.
H. GNU Affero General Public License version 3
Version 3, 19 November 2007
Copyright © 2007 Free Software Foundation, Inc. https://fsf.org/
Everyone is permitted to copy and distribute verbatim copies of this
license document, but changing it is not allowed.
Preamble
The GNU Affero General Public License is a free, copyleft license for
software and other kinds of works, specifically designed to ensure
cooperation with the community in the case of network server software.
The licenses for most software and other practical works are designed to
take away your freedom to share and change the works. By contrast, our
General Public Licenses are intended to guarantee your freedom to share
and change all versions of a program--to make sure it remains free
software for all its users.
When we speak of free software, we are referring to freedom, not price.
Our General Public Licenses are designed to make sure that you have the
freedom to distribute copies of free software (and charge for them if you
wish), that you receive source code or can get it if you want it, that you
can change the software or use pieces of it in new free programs, and that
you know you can do these things.
Developers that use our General Public Licenses protect your rights with
two steps: (1) assert copyright on the software, and (2) offer you this
License which gives you legal permission to copy, distribute and/or modify
the software.
A secondary benefit of defending all users' freedom is that improvements
made in alternate versions of the program, if they receive widespread use,
become available for other developers to incorporate. Many developers of
free software are heartened and encouraged by the resulting cooperation.
However, in the case of software used on network servers, this result may
fail to come about. The GNU General Public License permits making a
modified version and letting the public access it on a server without ever
releasing its source code to the public.
The GNU Affero General Public License is designed specifically to ensure
that, in such cases, the modified source code becomes available to the
community. It requires the operator of a network server to provide the
source code of the modified version running there to the users of that
server. Therefore, public use of a modified version, on a publicly
accessible server, gives the public access to the source code of the
modified version.
An older license, called the Affero General Public License and published
by Affero, was designed to accomplish similar goals. This is a different
license, not a version of the Affero GPL, but Affero has released a new
version of the Affero GPL which permits relicensing under this license.
The precise terms and conditions for copying, distribution and
modification follow.
TERMS AND CONDITIONS
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“This License” refers to version 3 of the GNU Affero General Public
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“Copyright” also means copyright-like laws that apply to other kinds of
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Notwithstanding any other provision of this License, if you modify the
Program, your modified version must prominently offer all users
interacting with it remotely through a computer network (if your version
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Notwithstanding any other provision of this License, you have permission
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17. Interpretation of Sections 15 and 16.
If the disclaimer of warranty and limitation of liability provided above
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END OF TERMS AND CONDITIONS
How to Apply These Terms to Your New Programs
If you develop a new program, and you want it to be of the greatest
possible use to the public, the best way to achieve this is to make it
free software which everyone can redistribute and change under these
terms.
To do so, attach the following notices to the program. It is safest to
attach them to the start of each source file to most effectively state the
exclusion of warranty; and each file should have at least the “copyright”
line and a pointer to where the full notice is found.
one line to give the program’s name and a brief idea of what it does.
Copyright (C) year name of author
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Affero General Public License for more details.
You should have received a copy of the GNU Affero General Public License
along with this program. If not, see https://www.gnu.org/licenses/.
Also add information on how to contact you by electronic and paper mail.
If your software can interact with users remotely through a computer
network, you should also make sure that it provides a way for users to get
its source. For example, if your program is a web application, its
interface could display a “Source” link that leads users to an archive of
the code. There are many ways you could offer source, and different
solutions will be better for different programs; see section 13 for the
specific requirements.
You should also get your employer (if you work as a programmer) or school,
if any, to sign a “copyright disclaimer” for the program, if necessary.
For more information on this, and how to apply and follow the GNU AGPL,
see https://www.gnu.org/licenses/.
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----------------------------------------------------------------------
^[1] The downside to installing in a schema is that when writing SQL you
must either set your search_path or qualify names, by prepending the
object name with the schema name and a period. For example, without
setting a search path, if you installed into a schema named isok, instead
of SELECT * FROM run_isok_queries();, you would have to write SELECT *
FROM isok.run_isok_queries();.
^[2] Possibly, the GNU m4 implementation is required. This is what
PostgreSQL requires, and alternatives have not been tested.
^[3] The unspecified PL/pgSQL behavior being, that the target in a
PL/pgSQL statement of the form “FOR target IN EXECUTE text_expression [
USING expression [, ... ] ] LOOP” is allowed to contain more variables
than the test_expression returns columns, in which case the extra
variables are assigned the NULL value. Because this behavior is
undocumented, it is subject to change. Should this behavior change,
returning a third column will be required, not optional.
^[4] To remove an ISOK_RESULTS.Deferred_To value and add a
ISOK_RESULTS.Resolved value without raising an error either update both
values in the same UPDATE statement or first set the Deferred_To value to
NULL and then the Resolved value to something non-NULL.
^[5] The time the current transaction started, which, if a transaction was
not explicitly started, is the time the database engine received the
current SQL statement from the client and began execution.
^[6] Yes, this is true of all objects. Only the owner has access to any
newly-created object. But having a single point of access, the schema
dedicated to Isok, that grants access to all of Isok, provides a very
useful point of control that serves as an easily audited gateway to Isok's
functionality.
^[7] See: Estimating the Total Development Cost of a Linux Distribution.
^[8] publicity or privacy — The use of a work free of known copyright
restrictions may be otherwise regulated or limited. The work or its use
may be subject to personal data protection laws, publicity, image, or
privacy rights that allow a person to control how their voice, image or
likeness is used, or other restrictions or limitations under applicable
law.
^[9] endorsement — In some jurisdictions, wrongfully implying that an
author, publisher or anyone else endorses your use of a work may be
unlawful.
