Skip to content
Projects
Groups
Snippets
Help
Loading...
Help
Support
Keyboard shortcuts
?
Submit feedback
Contribute to GitLab
Sign in
Toggle navigation
P
Postgres FD Implementation
Project overview
Project overview
Details
Activity
Releases
Repository
Repository
Files
Commits
Branches
Tags
Contributors
Graph
Compare
Issues
0
Issues
0
List
Boards
Labels
Milestones
Merge Requests
0
Merge Requests
0
CI / CD
CI / CD
Pipelines
Jobs
Schedules
Analytics
Analytics
CI / CD
Repository
Value Stream
Wiki
Wiki
Snippets
Snippets
Members
Members
Collapse sidebar
Close sidebar
Activity
Graph
Create a new issue
Jobs
Commits
Issue Boards
Open sidebar
Abuhujair Javed
Postgres FD Implementation
Commits
a6ca6525
Commit
a6ca6525
authored
Jul 20, 1998
by
Bruce Momjian
Browse files
Options
Browse Files
Download
Email Patches
Plain Diff
Update version.
parent
60baf183
Changes
1
Hide whitespace changes
Inline
Side-by-side
Showing
1 changed file
with
14 additions
and
1 deletion
+14
-1
src/tools/backend/index.html
src/tools/backend/index.html
+14
-1
No files found.
src/tools/backend/index.html
View file @
a6ca6525
...
...
@@ -10,6 +10,7 @@ How PostgreSQL Processes a Query
by Bruce Momjian
</H2>
<P>
A query comes to the backend via data packets arriving through TCP/IP
or Unix Domain sockets. It is loaded into a string, and passed to
the
...
...
@@ -22,12 +23,14 @@ identify the query type, and load the proper query-specific structure,
like
<A
HREF=
"../../include/nodes/parsenodes.h"
>
CreateStmt
</A>
or
<A
HREF=
"../../include/nodes/parsenodes.h"
>
SelectStmt.
</A>
<P>
The query is then identified as a
<I>
Utility
</I>
query or a more complex
query. A
<I>
Utility
</I>
query is processed by a query-specific function
in
<A
HREF=
"../../backend/commands"
>
commands.
</A>
A complex query, like
<I>
SELECT, UPDATE,
</I>
and
<I>
DELETE
</I>
requires much more handling.
<P>
The parser takes a complex query, and creates a
<A
HREF=
"../../include/nodes/parsenodes.h"
>
Query
</A>
structure that
contains all the elements used by complex queries. Query.qual holds the
...
...
@@ -39,6 +42,7 @@ are linked together to form the <I>range table</I> of the query, which is
generated by
<A
HREF=
"../../backend/parser/parse_clause.c"
>
makeRangeTable().
</A>
Query.rtable holds the query's range table.
<P>
Certain queries, like
<I>
SELECT,
</I>
return columns of data. Other
queries, like
<I>
INSERT
</I>
and
<I>
UPDATE,
</I>
specify the columns
modified by the query. These column references are converted to
<A
...
...
@@ -49,13 +53,16 @@ the query. The target list is stored in Query.targetList, which is
generated by
<A
HREF=
"../../backend/parser/parse_target.c"
>
transformTargetList().
</A>
<P>
Other query elements, like aggregates(
<I>
SUM()
</I>
),
<I>
GROUP BY,
</I>
and
<I>
ORDER BY
</I>
are also stored in their own Query fields.
<P>
The next step is for the Query to be modified by any
<I>
VIEWS
</I>
or
<I>
RULES
</I>
that may apply to the query. This is performed by the
<A
HREF=
"../../backend/rewrite"
>
rewrite
</A>
system.
<P>
The
<A
HREF=
"../../backend/optimizer"
>
optimizer
</A>
takes the Query
structure and generates an optimal
<A
HREF=
"../..//include/nodes/plannodes.h"
>
Plan,
</A>
which contains the
...
...
@@ -65,18 +72,21 @@ table join order and join type of each table in the RangeTable, using
Query.qual(
<I>
WHERE
</I>
clause) to consider optimal index usage.
<P>
The Plan is then passed to the
<A
HREF=
"../../backend/executor"
>
executor
</A>
for execution, and the result
returned to the client. The Plan actually as set of nodes, arranged in
a tree structure with a top-level node, and various sub-nodes as
children.
<P>
There are many other modules that support this basic functionality.
They can be accessed by clicking on the flowchart.
<P>
<HR>
<P>
<CENTER>
<EM><BIG>
Click on an item to see more detail or look at the full
...
...
@@ -107,8 +117,10 @@ Click on an item to see more detail or look at the full
</MAP>
<BR>
<P>
<HR>
<P>
Another area of interest is the shared memory area, which contains data
accessable to all backends. It has table recently used data/index
blocks, locks, backend information, and lookup tables for these
...
...
@@ -147,6 +159,7 @@ HREF="../../backend/storage/ipc/shmem.c">ShmemInitStruct(),</A> and
the lookups are created by
<A
HREF=
"../../backend/storage/ipc/shmem.c"
>
ShmemInitHash().
</A>
<P>
<HR
SIZE=
"2"
NOSHADE
>
<SMALL>
<ADDRESS>
...
...
Write
Preview
Markdown
is supported
0%
Try again
or
attach a new file
Attach a file
Cancel
You are about to add
0
people
to the discussion. Proceed with caution.
Finish editing this message first!
Cancel
Please
register
or
sign in
to comment