mirror of https://github.com/citusdata/citus.git
f4242685e3
In preprocess phase, we save the original database name, replace dbname field of CreatedbStmt with a temporary name (to let Postgres to create the database with the temporary name locally) and then we insert a cleanup record for the temporary database name on all nodes **(\*\*)**. And in postprocess phase, we first rename the temporary database back to its original name for local node and then return a list of distributed DDL jobs i) to create the database with the temporary name and then ii) to rename it back to its original name on other nodes. That way, if CREATE DATABASE fails on any of the nodes, the temporary database will be cleaned up by the cleanup records that we inserted in preprocess phase and in case of a failure, we won't leak any databases called as the name that user intended to use for the database. Solves the problem documented in https://github.com/citusdata/citus/issues/7369 for CREATE DATABASE commands. **(\*\*):** To ensure that we insert cleanup records on all nodes, with this PR we also start requiring having the coordinator in the metadata because otherwise we would skip inserting a cleanup record for the coordinator. |
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|---|---|---|
| .. | ||
| README.md | ||
| alter_table.c | ||
| begin.c | ||
| call.c | ||
| cascade_table_operation_for_connected_relations.c | ||
| citus_add_local_table_to_metadata.c | ||
| citus_global_signal.c | ||
| cluster.c | ||
| collation.c | ||
| comment.c | ||
| common.c | ||
| create_distributed_table.c | ||
| database.c | ||
| dependencies.c | ||
| distribute_object_ops.c | ||
| domain.c | ||
| drop_distributed_table.c | ||
| extension.c | ||
| foreign_constraint.c | ||
| foreign_data_wrapper.c | ||
| foreign_server.c | ||
| function.c | ||
| grant.c | ||
| index.c | ||
| index_pg_source.c | ||
| local_multi_copy.c | ||
| multi_copy.c | ||
| owned.c | ||
| policy.c | ||
| publication.c | ||
| rename.c | ||
| role.c | ||
| schema.c | ||
| schema_based_sharding.c | ||
| seclabel.c | ||
| sequence.c | ||
| statistics.c | ||
| subscription.c | ||
| table.c | ||
| text_search.c | ||
| trigger.c | ||
| truncate.c | ||
| type.c | ||
| utility_hook.c | ||
| vacuum.c | ||
| variableset.c | ||
| view.c | ||
README.md
Commands
The commands module is modeled after backend/commands from the postgres repository and
contains the logic for Citus on how to run these commands on distributed objects. Even
though the structure of the directory has some resemblence to its postgres relative, files
here are somewhat more fine-grained. This is due to the nature of citus commands that are
heavily focused on distributed tables. Instead of having all commands in tablecmds.c
they are often moved to files that are named after the command.
| File | Description |
|---|---|
create_distributed_table.c |
Implementation of UDF's for creating distributed tables |
drop_distributed_table.c |
Implementation for dropping metadata for partitions of distributed tables |
extension.c |
Implementation of CREATE EXTENSION commands for citus specific checks |
foreign_constraint.c |
Implementation of and helper functions for foreign key constraints |
grant.c |
Implementation of GRANT commands for roles/users on relations |
index.c |
Implementation of commands specific to indices on distributed tables |
multi_copy.c |
Implementation of COPY command. There are multiple different copy modes which are described in detail below |
policy.c |
Implementation of CREATE\ALTER POLICY commands. |
rename.c |
Implementation of ALTER ... RENAME ... commands. It implements the renaming of applicable objects, otherwise provides the user with a warning |
schema.c |
|
sequence.c |
Implementation of CREATE/ALTER SEQUENCE commands. Primarily checks correctness of sequence statements as they are not propagated to the worker nodes |
table.c |
|
transmit.c |
Implementation of COPY commands with format transmit set in the options. This format is used to transfer files from one node to another node |
truncate.c |
Implementation of TRUNCATE commands on distributed tables |
utility_hook.c |
This is the entry point from postgres into the commands module of citus. It contains the implementation that gets registered in postgres' ProcessUtility_hook callback to extends the functionality of the original ProcessUtility. This code is used to route the incoming commands to their respective implementation in Citus |
vacuum.c |
Implementation of VACUUM commands on distributed tables |
COPY
The copy command is overloaded for a couple of use-cases specific to citus. The syntax of the command stays the same, however the implementation might slightly differ from the stock implementation. The overloading is mostly done via extra options that Citus uses to indicate how to operate the copy. The options used are described below.
FORMAT transmit
Implemented in transmit.c
TODO: to be written by someone with enough knowledge to write how, when and why it is used.
FORMAT result
Implemented in multi_copy.c
TODO: to be written by someone with enough knowledge to write how, when and why it is used.