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When CREATE INDEX is run on a partitioned table, create catalog entries
for an index on the partitioned table (which is just a placeholder since
the table proper has no data of its own), and recurse to create actual
indexes on the existing partitions; create them in future partitions
also.
As a convenience gadget, if the new index definition matches some
existing index in partitions, these are picked up and used instead of
creating new ones. Whichever way these indexes come about, they become
attached to the index on the parent table and are dropped alongside it,
and cannot be dropped on isolation unless they are detached first.
To support pg_dump'ing these indexes, add commands
CREATE INDEX ON ONLY <table>
(which creates the index on the parent partitioned table, without
recursing) and
ALTER INDEX ATTACH PARTITION
(which is used after the indexes have been created individually on each
partition, to attach them to the parent index). These reconstruct prior
database state exactly.
Reviewed-by: (in alphabetical order) Peter Eisentraut, Robert Haas, Amit
Langote, Jesper Pedersen, Simon Riggs, David Rowley
Discussion: https://postgr.es/m/20171113170646.gzweigyrgg6pwsg4@alvherre.pgsql
src/backend/nodes/README
Node Structures
===============
Andrew Yu (11/94)
Introduction
------------
The current node structures are plain old C structures. "Inheritance" is
achieved by convention. No additional functions will be generated. Functions
that manipulate node structures reside in this directory.
FILES IN THIS DIRECTORY (src/backend/nodes/)
General-purpose node manipulation functions:
copyfuncs.c - copy a node tree
equalfuncs.c - compare two node trees
outfuncs.c - convert a node tree to text representation
readfuncs.c - convert text representation back to a node tree
makefuncs.c - creator functions for some common node types
nodeFuncs.c - some other general-purpose manipulation functions
Specialized manipulation functions:
bitmapset.c - Bitmapset support
list.c - generic list support
params.c - Param support
tidbitmap.c - TIDBitmap support
value.c - support for Value nodes
FILES IN src/include/nodes/
Node definitions:
nodes.h - define node tags (NodeTag)
primnodes.h - primitive nodes
parsenodes.h - parse tree nodes
plannodes.h - plan tree nodes
relation.h - planner internal nodes
execnodes.h - executor nodes
memnodes.h - memory nodes
pg_list.h - generic list
Steps to Add a Node
-------------------
Suppose you want to define a node Foo:
1. Add a tag (T_Foo) to the enum NodeTag in nodes.h. (If you insert the
tag in a way that moves the numbers associated with existing tags,
you'll need to recompile the whole tree after doing this. It doesn't
force initdb though, because the numbers never go to disk.)
2. Add the structure definition to the appropriate include/nodes/???.h file.
If you intend to inherit from, say a Plan node, put Plan as the first field
of your struct definition.
3. If you intend to use copyObject, equal, nodeToString or stringToNode,
add an appropriate function to copyfuncs.c, equalfuncs.c, outfuncs.c
and readfuncs.c accordingly. (Except for frequently used nodes, don't
bother writing a creator function in makefuncs.c) The header comments
in those files give general rules for whether you need to add support.
4. Add cases to the functions in nodeFuncs.c as needed. There are many
other places you'll probably also need to teach about your new node
type. Best bet is to grep for references to one or two similar existing
node types to find all the places to touch.
Historical Note
---------------
Prior to the current simple C structure definitions, the Node structures
used a pseudo-inheritance system which automatically generated creator and
accessor functions. Since every node inherited from LispValue, the whole thing
was a mess. Here's a little anecdote:
LispValue definition -- class used to support lisp structures
in C. This is here because we did not want to totally rewrite
planner and executor code which depended on lisp structures when
we ported postgres V1 from lisp to C. -cim 4/23/90