Isolation tests
===============
-This directory contains a set of tests for the serializable isolation level.
-Testing isolation requires running multiple overlapping transactions,
-which requires multiple concurrent connections, and therefore can't be
-tested using the normal pg_regress program.
+This directory contains a set of tests for concurrent behaviors in
+PostgreSQL. These tests require running multiple interacting transactions,
+which requires management of multiple concurrent connections, and therefore
+can't be tested using the normal pg_regress program. The name "isolation"
+comes from the fact that the original motivation was to test the
+serializable isolation level; but tests for other sorts of concurrent
+behaviors have been added as well.
To run the tests, you need to have a server running at the default port
expected by libpq. (You can set PGPORT and so forth in your environment
to control this.) Then run
gmake installcheck
-Note that the prepared-transactions test will not pass unless you have
-the server's max_prepared_transactions parameter set to at least 3.
+To run just specific test(s), you can do something like
+ ./pg_isolation_regress fk-contention fk-deadlock
+(look into the specs/ subdirectory to see the available tests).
-To represent a test with overlapping transactions, we use a test specification
-file with a custom syntax, which is described in the next section.
+The prepared-transactions test requires the server's
+max_prepared_transactions parameter to be set to at least 3; therefore it
+is not run by default. To include it in the test run, use
+ gmake installcheck-prepared-txns
+
+To define tests with overlapping transactions, we use test specification
+files with a custom syntax, which is described in the next section. To add
+a new test, place a spec file in the specs/ subdirectory, add the expected
+output in the expected/ subdirectory, and add the test's name to the
+isolation_schedule file.
isolationtester is a program that uses libpq to open multiple connections,
and executes a test specified by a spec file. A libpq connection string
environment variables are used otherwise.
pg_isolation_regress is a tool similar to pg_regress, but instead of using
-psql to execute a test, it uses isolationtester.
+psql to execute a test, it uses isolationtester. It accepts all the same
+command-line arguments as pg_regress.
Test specification
setup { <SQL> }
The given SQL block is executed once, in one session only, before running
- the test. Create any test tables or such objects here. This part is
- optional.
+ the test. Create any test tables or other required objects here. This
+ part is optional.
teardown { <SQL> }
The teardown SQL block is executed once after the test is finished. Use
- this to clean up, e.g dropping any test tables. This part is optional.
+ this to clean up in preparation for the next permutation, e.g dropping
+ any test tables created by setup. This part is optional.
session "<name>"
- Each session is executed in a separate connection. A session consists
- of four parts: setup, teardown and one or more steps. The per-session
+ There are normally several "session" parts in a spec file. Each
+ session is executed in its own connection. A session part consists
+ of three parts: setup, teardown and one or more "steps". The per-session
setup and teardown parts have the same syntax as the per-test setup and
- teardown described above, but they are executed in every session,
- before and after each permutation. The setup part typically contains a
- "BEGIN" command to begin a transaction.
+ teardown described above, but they are executed in each session. The
+ setup part typically contains a "BEGIN" command to begin a transaction.
- Each step has a syntax of
+ Each step has the syntax
step "<name>" { <SQL> }
- where <name> is a unique name identifying this step, and SQL is a SQL
- statement (or statements, separated by semicolons) that is executed in the
- step.
+ where <name> is a name identifying this step, and SQL is a SQL statement
+ (or statements, separated by semicolons) that is executed in the step.
+ Step names must be unique across the whole spec file.
permutation "<step name>" ...
A permutation line specifies a list of steps that are run in that order.
- If no permutation lines are given, the test program automatically generates
- all possible overlapping orderings of the given sessions.
+ Any number of permutation lines can appear. If no permutation lines are
+ given, the test program automatically generates all possible orderings
+ of the steps from each session (running the steps of any one session in
+ order). Note that the list of steps in a manually specified
+ "permutation" line doesn't actually have to be a permutation of the
+ available steps; it could for instance repeat some steps more than once,
+ or leave others out.
Lines beginning with a # are considered comments.
+For each permutation of the session steps (whether these are manually
+specified in the spec file, or automatically generated), the isolation
+tester runs the main setup part, then per-session setup parts, then
+the selected session steps, then per-session teardown, then the main
+teardown script. Each selected step is sent to the connection associated
+with its session.
+
Support for blocking commands
=============================
-Each spec may contain commands that block until further action has been taken
+Each step may contain commands that block until further action has been taken
(most likely, some other session runs a step that unblocks it or causes a
-deadlock). Such a spec needs to be careful to manually specify valid
+deadlock). A test that uses this ability must manually specify valid
permutations, i.e. those that would not expect a blocked session to execute a
-command. If the spec fails to follow that rule, the spec is aborted.
+command. If the test fails to follow that rule, the test is aborted.
+
+Currently, at most one step can be waiting at a time. As long as one
+step is waiting, subsequent steps are run to completion synchronously.
-Only one command can be waiting at a time. As long as one command is waiting,
-other commands are run to completion synchronously.
+Note that isolationtester recognizes that a command has blocked by looking
+to see if it is shown as waiting in the pg_locks view; therefore, only
+blocks on heavyweight locks will be detected.
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