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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>75.2. System Catalog Initial Data</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="system-catalog-declarations.html" title="75.1. System Catalog Declaration Rules" /><link rel="next" href="bki-format.html" title="75.3. BKI File Format" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">75.2. System Catalog Initial Data</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="system-catalog-declarations.html" title="75.1. System Catalog Declaration Rules">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="bki.html" title="Chapter 75. System Catalog Declarations and Initial Contents">Up</a></td><th width="60%" align="center">Chapter 75. System Catalog Declarations and Initial Contents</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 16.3 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="bki-format.html" title="75.3. BKI File Format">Next</a></td></tr></table><hr /></div><div class="sect1" id="SYSTEM-CATALOG-INITIAL-DATA"><div class="titlepage"><div><div><h2 class="title" style="clear: both">75.2. System Catalog Initial Data <a href="#SYSTEM-CATALOG-INITIAL-DATA" class="id_link">#</a></h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="sect2"><a href="system-catalog-initial-data.html#SYSTEM-CATALOG-INITIAL-DATA-FORMAT">75.2.1. Data File Format</a></span></dt><dt><span class="sect2"><a href="system-catalog-initial-data.html#SYSTEM-CATALOG-OID-ASSIGNMENT">75.2.2. OID Assignment</a></span></dt><dt><span class="sect2"><a href="system-catalog-initial-data.html#SYSTEM-CATALOG-OID-REFERENCES">75.2.3. OID Reference Lookup</a></span></dt><dt><span class="sect2"><a href="system-catalog-initial-data.html#SYSTEM-CATALOG-AUTO-ARRAY-TYPES">75.2.4. Automatic Creation of Array Types</a></span></dt><dt><span class="sect2"><a href="system-catalog-initial-data.html#SYSTEM-CATALOG-RECIPES">75.2.5. Recipes for Editing Data Files</a></span></dt></dl></div><p>
Each catalog that has any manually-created initial data (some do not)
has a corresponding <code class="literal">.dat</code> file that contains its
initial data in an editable format.
</p><div class="sect2" id="SYSTEM-CATALOG-INITIAL-DATA-FORMAT"><div class="titlepage"><div><div><h3 class="title">75.2.1. Data File Format <a href="#SYSTEM-CATALOG-INITIAL-DATA-FORMAT" class="id_link">#</a></h3></div></div></div><p>
Each <code class="literal">.dat</code> file contains Perl data structure literals
that are simply eval'd to produce an in-memory data structure consisting
of an array of hash references, one per catalog row.
A slightly modified excerpt from <code class="filename">pg_database.dat</code>
will demonstrate the key features:
</p><pre class="programlisting">
[
# A comment could appear here.
{ oid => '1', oid_symbol => 'Template1DbOid',
descr => 'database\'s default template',
datname => 'template1', encoding => 'ENCODING',
datlocprovider => 'LOCALE_PROVIDER', datistemplate => 't',
datallowconn => 't', datconnlimit => '-1', datfrozenxid => '0',
datminmxid => '1', dattablespace => 'pg_default', datcollate => 'LC_COLLATE',
datctype => 'LC_CTYPE', daticulocale => 'ICU_LOCALE', datacl => '_null_' },
]
</pre><p>
Points to note:
</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
The overall file layout is: open square bracket, one or more sets of
curly braces each of which represents a catalog row, close square
bracket. Write a comma after each closing curly brace.
</p></li><li class="listitem"><p>
Within each catalog row, write comma-separated
<em class="replaceable"><code>key</code></em> <code class="literal">=></code>
<em class="replaceable"><code>value</code></em> pairs. The
allowed <em class="replaceable"><code>key</code></em>s are the names of the catalog's
columns, plus the metadata keys <code class="literal">oid</code>,
<code class="literal">oid_symbol</code>,
<code class="literal">array_type_oid</code>, and <code class="literal">descr</code>.
(The use of <code class="literal">oid</code> and <code class="literal">oid_symbol</code>
is described in <a class="xref" href="system-catalog-initial-data.html#SYSTEM-CATALOG-OID-ASSIGNMENT" title="75.2.2. OID Assignment">Section 75.2.2</a> below,
while <code class="literal">array_type_oid</code> is described in
<a class="xref" href="system-catalog-initial-data.html#SYSTEM-CATALOG-AUTO-ARRAY-TYPES" title="75.2.4. Automatic Creation of Array Types">Section 75.2.4</a>.
<code class="literal">descr</code> supplies a description string for the object,
which will be inserted into <code class="structname">pg_description</code>
or <code class="structname">pg_shdescription</code> as appropriate.)
While the metadata keys are optional, the catalog's defined columns
must all be provided, except when the catalog's <code class="literal">.h</code>
file specifies a default value for the column.
(In the example above, the <code class="structfield">datdba</code> field has
been omitted because <code class="filename">pg_database.h</code> supplies a
suitable default value for it.)
</p></li><li class="listitem"><p>
All values must be single-quoted. Escape single quotes used within a
value with a backslash. Backslashes meant as data can, but need not,
be doubled; this follows Perl's rules for simple quoted literals.
Note that backslashes appearing as data will be treated as escapes by
the bootstrap scanner, according to the same rules as for escape string
constants (see <a class="xref" href="sql-syntax-lexical.html#SQL-SYNTAX-STRINGS-ESCAPE" title="4.1.2.2. String Constants with C-Style Escapes">Section 4.1.2.2</a>); for
example <code class="literal">\t</code> converts to a tab character. If you
actually want a backslash in the final value, you will need to write
four of them: Perl strips two, leaving <code class="literal">\\</code> for the
bootstrap scanner to see.
</p></li><li class="listitem"><p>
Null values are represented by <code class="literal">_null_</code>.
(Note that there is no way to create a value that is just that
string.)
</p></li><li class="listitem"><p>
Comments are preceded by <code class="literal">#</code>, and must be on their
own lines.
</p></li><li class="listitem"><p>
Field values that are OIDs of other catalog entries should be
represented by symbolic names rather than actual numeric OIDs.
(In the example above, <code class="structfield">dattablespace</code>
contains such a reference.)
This is described in <a class="xref" href="system-catalog-initial-data.html#SYSTEM-CATALOG-OID-REFERENCES" title="75.2.3. OID Reference Lookup">Section 75.2.3</a>
below.
</p></li><li class="listitem"><p>
Since hashes are unordered data structures, field order and line
layout aren't semantically significant. However, to maintain a
consistent appearance, we set a few rules that are applied by the
formatting script <code class="filename">reformat_dat_file.pl</code>:
</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>
Within each pair of curly braces, the metadata
fields <code class="literal">oid</code>, <code class="literal">oid_symbol</code>,
<code class="literal">array_type_oid</code>, and <code class="literal">descr</code>
(if present) come first, in that order, then the catalog's own
fields appear in their defined order.
</p></li><li class="listitem"><p>
Newlines are inserted between fields as needed to limit line length
to 80 characters, if possible. A newline is also inserted between
the metadata fields and the regular fields.
</p></li><li class="listitem"><p>
If the catalog's <code class="literal">.h</code> file specifies a default
value for a column, and a data entry has that same
value, <code class="filename">reformat_dat_file.pl</code> will omit it from
the data file. This keeps the data representation compact.
</p></li><li class="listitem"><p>
<code class="filename">reformat_dat_file.pl</code> preserves blank lines
and comment lines as-is.
</p></li></ul></div><p>
It's recommended to run <code class="filename">reformat_dat_file.pl</code>
before submitting catalog data patches. For convenience, you can
simply change to <code class="filename">src/include/catalog/</code> and
run <code class="literal">make reformat-dat-files</code>.
</p></li><li class="listitem"><p>
If you want to add a new method of making the data representation
smaller, you must implement it
in <code class="filename">reformat_dat_file.pl</code> and also
teach <code class="function">Catalog::ParseData()</code> how to expand the
data back into the full representation.
</p></li></ul></div></div><div class="sect2" id="SYSTEM-CATALOG-OID-ASSIGNMENT"><div class="titlepage"><div><div><h3 class="title">75.2.2. OID Assignment <a href="#SYSTEM-CATALOG-OID-ASSIGNMENT" class="id_link">#</a></h3></div></div></div><p>
A catalog row appearing in the initial data can be given a
manually-assigned OID by writing an <code class="literal">oid
=> <em class="replaceable"><code>nnnn</code></em></code> metadata field.
Furthermore, if an OID is assigned, a C macro for that OID can be
created by writing an <code class="literal">oid_symbol
=> <em class="replaceable"><code>name</code></em></code> metadata field.
</p><p>
Pre-loaded catalog rows must have preassigned OIDs if there are OID
references to them in other pre-loaded rows. A preassigned OID is
also needed if the row's OID must be referenced from C code.
If neither case applies, the <code class="literal">oid</code> metadata field can
be omitted, in which case the bootstrap code assigns an OID
automatically.
In practice we usually preassign OIDs for all or none of the pre-loaded
rows in a given catalog, even if only some of them are actually
cross-referenced.
</p><p>
Writing the actual numeric value of any OID in C code is considered
very bad form; always use a macro, instead. Direct references
to <code class="structname">pg_proc</code> OIDs are common enough that there's
a special mechanism to create the necessary macros automatically;
see <code class="filename">src/backend/utils/Gen_fmgrtab.pl</code>. Similarly
— but, for historical reasons, not done the same way —
there's an automatic method for creating macros
for <code class="structname">pg_type</code>
OIDs. <code class="literal">oid_symbol</code> entries are therefore not
necessary in those two catalogs. Likewise, macros for
the <code class="structname">pg_class</code> OIDs of system catalogs and
indexes are set up automatically. For all other system catalogs, you
have to manually specify any macros you need
via <code class="literal">oid_symbol</code> entries.
</p><p>
To find an available OID for a new pre-loaded row, run the
script <code class="filename">src/include/catalog/unused_oids</code>.
It prints inclusive ranges of unused OIDs (e.g., the output
line <code class="literal">45-900</code> means OIDs 45 through 900 have not been
allocated yet). Currently, OIDs 1–9999 are reserved for manual
assignment; the <code class="filename">unused_oids</code> script simply looks
through the catalog headers and <code class="filename">.dat</code> files
to see which ones do not appear. You can also use
the <code class="filename">duplicate_oids</code> script to check for mistakes.
(<code class="filename">genbki.pl</code> will assign OIDs for any rows that
didn't get one hand-assigned to them, and it will also detect duplicate
OIDs at compile time.)
</p><p>
When choosing OIDs for a patch that is not expected to be committed
immediately, best practice is to use a group of more-or-less
consecutive OIDs starting with some random choice in the range
8000—9999. This minimizes the risk of OID collisions with other
patches being developed concurrently. To keep the 8000—9999
range free for development purposes, after a patch has been committed
to the master git repository its OIDs should be renumbered into
available space below that range. Typically, this will be done
near the end of each development cycle, moving all OIDs consumed by
patches committed in that cycle at the same time. The script
<code class="filename">renumber_oids.pl</code> can be used for this purpose.
If an uncommitted patch is found to have OID conflicts with some
recently-committed patch, <code class="filename">renumber_oids.pl</code> may
also be useful for recovering from that situation.
</p><p>
Because of this convention of possibly renumbering OIDs assigned by
patches, the OIDs assigned by a patch should not be considered stable
until the patch has been included in an official release. We do not
change manually-assigned object OIDs once released, however, as that
would create assorted compatibility problems.
</p><p>
If <code class="filename">genbki.pl</code> needs to assign an OID to a catalog
entry that does not have a manually-assigned OID, it will use a value in
the range 10000—11999. The server's OID counter is set to 10000
at the start of a bootstrap run, so that any objects created on-the-fly
during bootstrap processing also receive OIDs in this range. (The
usual OID assignment mechanism takes care of preventing any conflicts.)
</p><p>
Objects with OIDs below <code class="symbol">FirstUnpinnedObjectId</code> (12000)
are considered <span class="quote">“<span class="quote">pinned</span>”</span>, preventing them from being
deleted. (There are a small number of exceptions, which are
hard-wired into <code class="function">IsPinnedObject()</code>.)
<span class="application">initdb</span> forces the OID counter up
to <code class="symbol">FirstUnpinnedObjectId</code> as soon as it's ready to
create unpinned objects. Thus objects created during the later phases
of <span class="application">initdb</span>, such as objects created while
running the <code class="filename">information_schema.sql</code> script, will
not be pinned, while all objects known
to <code class="filename">genbki.pl</code> will be.
</p><p>
OIDs assigned during normal database operation are constrained to be
16384 or higher. This ensures that the range 10000—16383 is free
for OIDs assigned automatically by <code class="filename">genbki.pl</code> or
during <span class="application">initdb</span>. These
automatically-assigned OIDs are not considered stable, and may change
from one installation to another.
</p></div><div class="sect2" id="SYSTEM-CATALOG-OID-REFERENCES"><div class="titlepage"><div><div><h3 class="title">75.2.3. OID Reference Lookup <a href="#SYSTEM-CATALOG-OID-REFERENCES" class="id_link">#</a></h3></div></div></div><p>
In principle, cross-references from one initial catalog row to another
could be written just by writing the preassigned OID of the referenced
row in the referencing field. However, that is against project
policy, because it is error-prone, hard to read, and subject to
breakage if a newly-assigned OID is renumbered. Therefore
<code class="filename">genbki.pl</code> provides mechanisms to write
symbolic references instead.
The rules are as follows:
</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
Use of symbolic references is enabled in a particular catalog column
by attaching <code class="literal">BKI_LOOKUP(<em class="replaceable"><code>lookuprule</code></em>)</code>
to the column's definition, where <em class="replaceable"><code>lookuprule</code></em>
is the name of the referenced catalog, e.g., <code class="literal">pg_proc</code>.
<code class="literal">BKI_LOOKUP</code> can be attached to columns of
type <code class="type">Oid</code>, <code class="type">regproc</code>, <code class="type">oidvector</code>,
or <code class="type">Oid[]</code>; in the latter two cases it implies performing a
lookup on each element of the array.
</p></li><li class="listitem"><p>
It's also permissible to attach <code class="literal">BKI_LOOKUP(encoding)</code>
to integer columns to reference character set encodings, which are
not currently represented as catalog OIDs, but have a set of values
known to <code class="filename">genbki.pl</code>.
</p></li><li class="listitem"><p>
In some catalog columns, it's allowed for entries to be zero instead
of a valid reference. If this is allowed, write
<code class="literal">BKI_LOOKUP_OPT</code> instead
of <code class="literal">BKI_LOOKUP</code>. Then you can
write <code class="literal">0</code> for an entry. (If the column is
declared <code class="type">regproc</code>, you can optionally
write <code class="literal">-</code> instead of <code class="literal">0</code>.)
Except for this special case, all entries in
a <code class="literal">BKI_LOOKUP</code> column must be symbolic references.
<code class="filename">genbki.pl</code> will warn about unrecognized names.
</p></li><li class="listitem"><p>
Most kinds of catalog objects are simply referenced by their names.
Note that type names must exactly match the
referenced <code class="structname">pg_type</code>
entry's <code class="structfield">typname</code>; you do not get to use
any aliases such as <code class="literal">integer</code>
for <code class="literal">int4</code>.
</p></li><li class="listitem"><p>
A function can be represented by
its <code class="structfield">proname</code>, if that is unique among
the <code class="filename">pg_proc.dat</code> entries (this works like regproc
input). Otherwise, write it
as <em class="replaceable"><code>proname(argtypename,argtypename,...)</code></em>,
like regprocedure. The argument type names must be spelled exactly as
they are in the <code class="filename">pg_proc.dat</code> entry's
<code class="structfield">proargtypes</code> field. Do not insert any
spaces.
</p></li><li class="listitem"><p>
Operators are represented
by <em class="replaceable"><code>oprname(lefttype,righttype)</code></em>,
writing the type names exactly as they appear in
the <code class="filename">pg_operator.dat</code>
entry's <code class="structfield">oprleft</code>
and <code class="structfield">oprright</code> fields.
(Write <code class="literal">0</code> for the omitted operand of a unary
operator.)
</p></li><li class="listitem"><p>
The names of opclasses and opfamilies are only unique within an
access method, so they are represented
by <em class="replaceable"><code>access_method_name</code></em><code class="literal">/</code><em class="replaceable"><code>object_name</code></em>.
</p></li><li class="listitem"><p>
In none of these cases is there any provision for
schema-qualification; all objects created during bootstrap are
expected to be in the <code class="literal">pg_catalog</code> schema.
</p></li></ul></div><p>
<code class="filename">genbki.pl</code> resolves all symbolic references while it
runs, and puts simple numeric OIDs into the emitted BKI file. There is
therefore no need for the bootstrap backend to deal with symbolic
references.
</p><p>
It's desirable to mark OID reference columns
with <code class="literal">BKI_LOOKUP</code> or <code class="literal">BKI_LOOKUP_OPT</code>
even if the catalog has no initial data that requires lookup. This
allows <code class="filename">genbki.pl</code> to record the foreign key
relationships that exist in the system catalogs. That information is
used in the regression tests to check for incorrect entries. See also
the macros <code class="literal">DECLARE_FOREIGN_KEY</code>,
<code class="literal">DECLARE_FOREIGN_KEY_OPT</code>,
<code class="literal">DECLARE_ARRAY_FOREIGN_KEY</code>,
and <code class="literal">DECLARE_ARRAY_FOREIGN_KEY_OPT</code>, which are
used to declare foreign key relationships that are too complex
for <code class="literal">BKI_LOOKUP</code> (typically, multi-column foreign
keys).
</p></div><div class="sect2" id="SYSTEM-CATALOG-AUTO-ARRAY-TYPES"><div class="titlepage"><div><div><h3 class="title">75.2.4. Automatic Creation of Array Types <a href="#SYSTEM-CATALOG-AUTO-ARRAY-TYPES" class="id_link">#</a></h3></div></div></div><p>
Most scalar data types should have a corresponding array type (that is,
a standard varlena array type whose element type is the scalar type, and
which is referenced by the <code class="structfield">typarray</code> field of
the scalar type's <code class="structname">pg_type</code>
entry). <code class="filename">genbki.pl</code> is able to generate
the <code class="structname">pg_type</code> entry for the array type
automatically in most cases.
</p><p>
To use this facility, just write an <code class="literal">array_type_oid
=> <em class="replaceable"><code>nnnn</code></em></code> metadata field in the
scalar type's <code class="structname">pg_type</code> entry, specifying the OID
to use for the array type. You may then omit
the <code class="structfield">typarray</code> field, since it will be filled
automatically with that OID.
</p><p>
The generated array type's name is the scalar type's name with an
underscore prepended. The array entry's other fields are filled from
<code class="literal">BKI_ARRAY_DEFAULT(<em class="replaceable"><code>value</code></em>)</code>
annotations in <code class="filename">pg_type.h</code>, or if there isn't one,
copied from the scalar type. (There's also a special case
for <code class="structfield">typalign</code>.) Then
the <code class="structfield">typelem</code>
and <code class="structfield">typarray</code> fields of the two entries are
set to cross-reference each other.
</p></div><div class="sect2" id="SYSTEM-CATALOG-RECIPES"><div class="titlepage"><div><div><h3 class="title">75.2.5. Recipes for Editing Data Files <a href="#SYSTEM-CATALOG-RECIPES" class="id_link">#</a></h3></div></div></div><p>
Here are some suggestions about the easiest ways to perform common tasks
when updating catalog data files.
</p><p><strong>Add a new column with a default to a catalog: </strong>
Add the column to the header file with
a <code class="literal">BKI_DEFAULT(<em class="replaceable"><code>value</code></em>)</code>
annotation. The data file need only be adjusted by adding the field
in existing rows where a non-default value is needed.
</p><p><strong>Add a default value to an existing column that doesn't have
one: </strong>
Add a <code class="literal">BKI_DEFAULT</code> annotation to the header file,
then run <code class="literal">make reformat-dat-files</code> to remove
now-redundant field entries.
</p><p><strong>Remove a column, whether it has a default or not: </strong>
Remove the column from the header, then run <code class="literal">make
reformat-dat-files</code> to remove now-useless field entries.
</p><p><strong>Change or remove an existing default value: </strong>
You cannot simply change the header file, since that will cause the
current data to be interpreted incorrectly. First run <code class="literal">make
expand-dat-files</code> to rewrite the data files with all
default values inserted explicitly, then change or remove
the <code class="literal">BKI_DEFAULT</code> annotation, then run <code class="literal">make
reformat-dat-files</code> to remove superfluous fields again.
</p><p><strong>Ad-hoc bulk editing: </strong>
<code class="filename">reformat_dat_file.pl</code> can be adapted to perform
many kinds of bulk changes. Look for its block comments showing where
one-off code can be inserted. In the following example, we are going
to consolidate two Boolean fields in <code class="structname">pg_proc</code>
into a char field:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>
Add the new column, with a default,
to <code class="filename">pg_proc.h</code>:
</p><pre class="programlisting">
+ /* see PROKIND_ categories below */
+ char prokind BKI_DEFAULT(f);
</pre><p>
</p></li><li class="listitem"><p>
Create a new script based on <code class="filename">reformat_dat_file.pl</code>
to insert appropriate values on-the-fly:
</p><pre class="programlisting">
- # At this point we have the full row in memory as a hash
- # and can do any operations we want. As written, it only
- # removes default values, but this script can be adapted to
- # do one-off bulk-editing.
+ # One-off change to migrate to prokind
+ # Default has already been filled in by now, so change to other
+ # values as appropriate
+ if ($values{proisagg} eq 't')
+ {
+ $values{prokind} = 'a';
+ }
+ elsif ($values{proiswindow} eq 't')
+ {
+ $values{prokind} = 'w';
+ }
</pre><p>
</p></li><li class="listitem"><p>
Run the new script:
</p><pre class="programlisting">
$ cd src/include/catalog
$ perl rewrite_dat_with_prokind.pl pg_proc.dat
</pre><p>
At this point <code class="filename">pg_proc.dat</code> has all three
columns, <code class="structfield">prokind</code>,
<code class="structfield">proisagg</code>,
and <code class="structfield">proiswindow</code>, though they will appear
only in rows where they have non-default values.
</p></li><li class="listitem"><p>
Remove the old columns from <code class="filename">pg_proc.h</code>:
</p><pre class="programlisting">
- /* is it an aggregate? */
- bool proisagg BKI_DEFAULT(f);
-
- /* is it a window function? */
- bool proiswindow BKI_DEFAULT(f);
</pre><p>
</p></li><li class="listitem"><p>
Finally, run <code class="literal">make reformat-dat-files</code> to remove
the useless old entries from <code class="filename">pg_proc.dat</code>.
</p></li></ol></div><p>
For further examples of scripts used for bulk editing, see
<code class="filename">convert_oid2name.pl</code>
and <code class="filename">remove_pg_type_oid_symbols.pl</code> attached to this
message:
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