NotificationsYou must be signed in to change notification settings
Fork6
Star31

Commit10fb290

committed

Document the system attributes ctid and tableoid, which for some reason

were never yet mentioned anywhere in our documentation. Improveexplanations of the other system attributes, too.

1 parent6334ef8 commit10fb290Copy full SHA for 10fb290

File tree

1 file changed

+45

-10

lines changed

doc/src/sgml
- syntax.sgml

1 file changed

+45

-10

lines changed

`‎doc/src/sgml/syntax.sgml‎`

Lines changed: 45 additions & 10 deletions

Original file line number	Diff line number	Diff line change
`@@ -1,5 +1,5 @@`
`1`	`1`	`<!--`
`2`		`-$Header: /cvsroot/pgsql/doc/src/sgml/syntax.sgml,v 1.32 2001/01/06 11:58:56 petere Exp $`
	`2`	`+$Header: /cvsroot/pgsql/doc/src/sgml/syntax.sgml,v 1.33 2001/01/08 22:07:47 tgl Exp $`
`3`	`3`	`-->`
`4`	`4`
`5`	`5`	`<chapter id="sql-syntax">`
`@@ -568,27 +568,33 @@ CAST ( '<replaceable>string</replaceable>' AS <replaceable>type</replaceable> )`
`568`	`568`	`<term>oid</term>`
`569`	`569`	`<listitem>`
`570`	`570`	`<para>`
`571`		`-stands for theunique identifier ofan instance whichisadded by`
`572`		`- Postgres to allinstances automatically. OIDs are not reused and are`
`573`		`- 32-bit quantities.`
	`571`	`+Theunique identifier(object ID)ofa row. Thisisa serial number`
	`572`	`+that is added byPostgres to allrows automatically. OIDs are not`
	`573`	`+reused and are32-bit quantities.`
`574`	`574`	`</para>`
`575`	`575`	`</listitem>`
`576`	`576`	`</varlistentry>`
`577`	`577`
`578`	`578`	`<varlistentry>`
`579`		`-<term>xmin</term>`
	`579`	`+ <term>tableoid</term>`
`580`	`580`	`<listitem>`
`581`	`581`	`<para>`
`582`		`- The identity of the inserting transaction.`
	`582`	`+ The OID of the table containing this row. This attribute is`
	`583`	`+ particularly handy for queries that select from inheritance`
	`584`	`+ hierarchies, since without it, it's difficult to tell which`
	`585`	`+ individual table a row came from. The tableoid can be joined`
	`586`	`+ against the OID attribute of pg_class to obtain the table name.`
`583`	`587`	`</para>`
`584`	`588`	`</listitem>`
`585`	`589`	`</varlistentry>`
`586`	`590`
`587`	`591`	`<varlistentry>`
`588`		`- <term>xmax</term>`
	`592`	`+<term>xmin</term>`
`589`	`593`	`<listitem>`
`590`	`594`	`<para>`
`591`		`- The identity of the deleting transaction.`
	`595`	`+ The identity (transaction ID) of the inserting transaction for`
	`596`	`+ this tuple. (Note: a tuple is an individual state of a row;`
	`597`	`+ each UPDATE of a row creates a new tuple for the same logical row.)`
`592`	`598`	`</para>`
`593`	`599`	`</listitem>`
`594`	`600`	`</varlistentry>`
`@@ -597,7 +603,19 @@ CAST ( '<replaceable>string</replaceable>' AS <replaceable>type</replaceable> )`
`597`	`603`	`<term>cmin</term>`
`598`	`604`	`<listitem>`
`599`	`605`	`<para>`
`600`		`- The command identifier within the inserting transaction.`
	`606`	`+ The command identifier (starting at zero) within the inserting`
	`607`	`+ transaction.`
	`608`	`+</para>`
	`609`	`+ </listitem>`
	`610`	`+ </varlistentry>`
	`611`	`+`
	`612`	`+ <varlistentry>`
	`613`	`+ <term>xmax</term>`
	`614`	`+ <listitem>`
	`615`	`+<para>`
	`616`	`+ The identity (transaction ID) of the deleting transaction,`
	`617`	`+ or zero for an undeleted tuple. In practice, this is never nonzero`
	`618`	`+ for a visible tuple.`
`601`	`619`	`</para>`
`602`	`620`	`</listitem>`
`603`	`621`	`</varlistentry>`
`@@ -606,7 +624,24 @@ CAST ( '<replaceable>string</replaceable>' AS <replaceable>type</replaceable> )`
`606`	`624`	`<term>cmax</term>`
`607`	`625`	`<listitem>`
`608`	`626`	`<para>`
`609`		`- The command identifier within the deleting transaction.`
	`627`	`+ The command identifier within the deleting transaction, or zero.`
	`628`	`+ Again, this is never nonzero for a visible tuple.`
	`629`	`+</para>`
	`630`	`+ </listitem>`
	`631`	`+ </varlistentry>`
	`632`	`+`
	`633`	`+ <varlistentry>`
	`634`	`+ <term>ctid</term>`
	`635`	`+ <listitem>`
	`636`	`+<para>`
	`637`	`+ The tuple ID of the tuple within its table. This is a pair`
	`638`	`+ (block number, tuple index within block) that identifies the`
	`639`	`+ physical location of the tuple. Note that although the ctid`
	`640`	`+ can be used to locate the tuple very quickly, a row's ctid`
	`641`	`+ will change each time it is updated or moved by VACUUM.`
	`642`	`+ Therefore ctid is useless as a long-term row identifier.`
	`643`	`+ The OID, or even better a user-defined serial number, should`
	`644`	`+ be used to identify logical rows.`
`610`	`645`	`</para>`
`611`	`646`	`</listitem>`
`612`	`647`	`</varlistentry>`

0 commit comments

Comments

(0)

Movatterモバイル変換

Navigation Menu

Search code, repositories, users, issues, pull requests...

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Uh oh!

Commit10fb290

File tree

1 file changed

1 file changed

`‎doc/src/sgml/syntax.sgml‎`

0 commit comments