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Implement SQL92-compatible FIRST, LAST, ABSOLUTE n, RELATIVE n options

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for FETCH and MOVE.
This commit is contained in:
Tom Lane 2003-03-11 19:40:24 +00:00
parent e4704001ea
commit 6261c75014
13 changed files with 669 additions and 387 deletions
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368
doc/src/sgml/ref/fetch.sgml
View file

@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/fetch.sgml,v 1.26 2003/03/10 03:53:49 tgl Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/fetch.sgml,v 1.27 2003/03/11 19:40:22 tgl Exp $
PostgreSQL documentation
-->
@ -18,17 +18,32 @@ PostgreSQL documentation
</refnamediv>
<refsynopsisdiv>
<refsynopsisdivinfo>
<date>1999-07-20</date>
<date>2003-03-11</date>
</refsynopsisdivinfo>
<synopsis>
FETCH [ <replaceable class="PARAMETER">direction</replaceable> ] [ <replaceable class="PARAMETER">count</replaceable> ] { IN | FROM } <replaceable class="PARAMETER">cursor</replaceable>
FETCH [ FORWARD | BACKWARD | RELATIVE ] [ <replaceable class="PARAMETER">#</replaceable> | ALL | NEXT | PRIOR ]
{ IN | FROM } <replaceable class="PARAMETER">cursor</replaceable>
FETCH [ <replaceable class="PARAMETER">direction</replaceable> { FROM | IN } ] <replaceable class="PARAMETER">cursor</replaceable>
where <replaceable class="PARAMETER">direction</replaceable> can be empty or one of:
NEXT
PRIOR
FIRST
LAST
ABSOLUTE <replaceable class="PARAMETER">count</replaceable>
RELATIVE <replaceable class="PARAMETER">count</replaceable>
<replaceable class="PARAMETER">count</replaceable>
ALL
FORWARD
FORWARD <replaceable class="PARAMETER">count</replaceable>
FORWARD ALL
BACKWARD
BACKWARD <replaceable class="PARAMETER">count</replaceable>
BACKWARD ALL
</synopsis>
<refsect2 id="R2-SQL-FETCH-1">
<refsect2info>
<date>1998-09-01</date>
<date>2003-03-11</date>
</refsect2info>
<title>
Inputs
@ -41,35 +56,151 @@ FETCH [ FORWARD | BACKWARD | RELATIVE ] [ <replaceable class="PARAMETER">#</repl
<listitem>
<para>
<replaceable class="PARAMETER">direction</replaceable>
defines the fetch direction. It can be one of
the following:
defines the fetch direction and number of rows to fetch.
It can be one of the following:
<variablelist>
<varlistentry>
<term>FORWARD</term>
<term>NEXT</term>
<listitem>
<para>
fetch next row(s). This is the default
fetch next row. This is the default
if <replaceable class="PARAMETER">direction</replaceable> is omitted.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>PRIOR</term>
<listitem>
<para>
fetch prior row.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>FIRST</term>
<listitem>
<para>
fetch first row of query (same as ABSOLUTE 1).
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>LAST</term>
<listitem>
<para>
fetch last row of query (same as ABSOLUTE -1).
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>ABSOLUTE <replaceable class="PARAMETER">count</replaceable></term>
<listitem>
<para>
fetch the <replaceable class="PARAMETER">count</replaceable>'th
row of query, or the
abs(<replaceable class="PARAMETER">count</replaceable>)'th row
from the end if
<replaceable class="PARAMETER">count</replaceable> &lt; 0.
Position before first row or after last row
if <replaceable class="PARAMETER">count</replaceable> is out of
range; in particular, ABSOLUTE 0 positions before first row.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>RELATIVE <replaceable class="PARAMETER">count</replaceable></term>
<listitem>
<para>
fetch the <replaceable class="PARAMETER">count</replaceable>'th
succeeding row, or the
abs(<replaceable class="PARAMETER">count</replaceable>)'th prior
row if <replaceable class="PARAMETER">count</replaceable> &lt; 0.
RELATIVE 0 re-fetches current row, if any.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="PARAMETER">count</replaceable></term>
<listitem>
<para>
fetch the next <replaceable class="PARAMETER">count</replaceable>
rows (same as FORWARD <replaceable class="PARAMETER">count</replaceable>).
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>ALL</term>
<listitem>
<para>
fetch all remaining rows (same as FORWARD ALL).
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>FORWARD</term>
<listitem>
<para>
fetch next row (same as NEXT).
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>FORWARD <replaceable class="PARAMETER">count</replaceable></term>
<listitem>
<para>
fetch next <replaceable class="PARAMETER">count</replaceable>
rows. FORWARD 0 re-fetches current row.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>FORWARD ALL</term>
<listitem>
<para>
fetch all remaining rows.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>BACKWARD</term>
<listitem>
<para>
fetch previous row(s).
fetch prior row (same as PRIOR).
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>RELATIVE</term>
<term>BACKWARD <replaceable class="PARAMETER">count</replaceable></term>
<listitem>
<para>
Same as FORWARD; provided for SQL92 compatibility.
fetch prior <replaceable class="PARAMETER">count</replaceable>
rows (scanning backwards). BACKWARD 0 re-fetches current row.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>BACKWARD ALL</term>
<listitem>
<para>
fetch all prior rows (scanning backwards).
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</listitem>
@ -80,53 +211,11 @@ FETCH [ FORWARD | BACKWARD | RELATIVE ] [ <replaceable class="PARAMETER">#</repl
<listitem>
<para>
<replaceable class="PARAMETER">count</replaceable>
determines how many rows to fetch. It can be one of the following:
<variablelist>
<varlistentry>
<term><replaceable class="PARAMETER">#</replaceable></term>
<listitem>
<para>
A signed integer constant that specifies how many rows to fetch.
Note that a negative integer is equivalent to changing the sense of
FORWARD and BACKWARD. Zero re-fetches the current row, if any.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
ALL
</term>
<listitem>
<para>
Retrieve all remaining rows.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
NEXT
</term>
<listitem>
<para>
Equivalent to specifying a count of <command>1</command>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
PRIOR
</term>
<listitem>
<para>
Equivalent to specifying a count of <command>-1</command>.
</para>
</listitem>
</varlistentry>
</variablelist>
is a possibly-signed integer constant, determining the location
or number of rows to fetch. For FORWARD and BACKWARD cases,
specifying a negative <replaceable
class="PARAMETER">count</replaceable>
is equivalent to changing the sense of FORWARD and BACKWARD.
</para>
</listitem>
</varlistentry>
@ -145,7 +234,7 @@ FETCH [ FORWARD | BACKWARD | RELATIVE ] [ <replaceable class="PARAMETER">#</repl
<refsect2 id="R2-SQL-FETCH-2">
<refsect2info>
<date>1998-04-15</date>
<date>2003-03-11</date>
</refsect2info>
<title>
Outputs
@ -162,25 +251,11 @@ WARNING: PerformPortalFetch: portal "<replaceable class="PARAMETER">cursor</rep
</computeroutput></term>
<listitem>
<para>
If <replaceable class="PARAMETER">cursor</replaceable>
is not previously declared.
The cursor must be declared within a transaction block.
If <replaceable class="PARAMETER">cursor</replaceable> is not known.
The cursor must have been declared within the current transaction block.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><computeroutput>
WARNING: FETCH/ABSOLUTE not supported, using RELATIVE
</computeroutput></term>
<listitem>
<para>
<productname>PostgreSQL</productname> does not support absolute
positioning of cursors.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
@ -188,75 +263,79 @@ WARNING: FETCH/ABSOLUTE not supported, using RELATIVE
<refsect1 id="R1-SQL-FETCH-1">
<refsect1info>
<date>1998-04-15</date>
<date>2003-03-11</date>
</refsect1info>
<title>
Description
</title>
<para>
<command>FETCH</command> allows a user to retrieve rows using a cursor.
The number of rows retrieved is specified by
<replaceable class="PARAMETER">#</replaceable>.
If the number of rows remaining in the cursor is less
than <replaceable class="PARAMETER">#</replaceable>,
then only those available are fetched.
Substituting the keyword ALL in place of a number will
cause all remaining rows in the cursor to be retrieved.
Rows may be fetched in both FORWARD and BACKWARD
directions. The default direction is FORWARD.
<command>FETCH</command> retrieves rows using a cursor.
</para>
<para>
The cursor position can be before the first row of the query result, or on
any particular row of the result, or after the last row of the result.
When created, a cursor is positioned before the first row. After fetching
some rows, the cursor is positioned on the last row retrieved. A new
<command>FETCH</command> always steps one row in the specified direction
(if possible) before beginning to return rows. If the
<command>FETCH</command> requests more rows than available, the cursor is
left positioned after the last row of the query result (or before the first
row, in the case of a backward fetch). This will always be the case after
<command>FETCH ALL</>.
A cursor has an associated <firstterm>position</> that is used by
<command>FETCH</>. The cursor position can be before the first row of the
query result, or on any particular row of the result, or after the last row
of the result. When created, a cursor is positioned before the first row.
After fetching some rows, the cursor is positioned on the row most recently
retrieved. If <command>FETCH</> runs off the end of the available rows
then the cursor is left positioned after the last row, or before the first
row if fetching backward. <command>FETCH ALL</> or <command>FETCH BACKWARD
ALL</> will always leave the cursor positioned after the last row or before
the first row.
</para>
<para>
The SQL-compatible forms (NEXT, PRIOR, FIRST, LAST, ABSOLUTE, RELATIVE)
fetch a single row after moving the cursor appropriately. If there is
no such row, an empty result is returned, and the cursor is left positioned
before the first row or after the last row as appropriate.
</para>
<para>
The forms using FORWARD and BACKWARD are not in the SQL standard, but
are <productname>PostgreSQL</productname> extensions. These forms
retrieve the indicated number of rows moving in the forward or backward
direction, leaving the cursor positioned on the last-returned row
(or after/before all rows, if the <replaceable
class="PARAMETER">count</replaceable> exceeds the number of rows
available).
</para>
<tip>
<para>
A zero row count requests fetching the current row without moving the
RELATIVE 0, FORWARD 0, and BACKWARD 0 all request
fetching the current row without moving the
cursor --- that is, re-fetching the most recently fetched row.
This will succeed unless the cursor is positioned before the
first row or after the last row; in which case, no row is returned.
</para>
</tip>
<tip>
<para>
Negative numbers are allowed to be specified for the
row count. A negative number is equivalent to reversing
the sense of the FORWARD and BACKWARD keywords. For example,
<command>FORWARD -1</command> is the same as <command>BACKWARD 1</command>.
</para>
</tip>
<refsect2 id="R2-SQL-FETCH-3">
<refsect2info>
<date>1998-04-15</date>
<date>2003-03-11</date>
</refsect2info>
<title>
Notes
</title>
<para>
A cursor to be used in backwards fetching should be declared with the
SCROLL option. In simple cases, <productname>PostgreSQL</productname>
will allow backwards fetch from cursors not declared with SCROLL, but
this behavior is best not relied on.
The cursor should be declared with the SCROLL option if one intends to
use any variants of <command>FETCH</> other than <command>FETCH NEXT</>
or <command>FETCH FORWARD</> with a positive count. For simple queries
<productname>PostgreSQL</productname> will allow backwards fetch from
cursors not declared with SCROLL, but this behavior is best not relied on.
</para>
<para>
The FORWARD, BACKWARD, and ALL keywords are
<productname>PostgreSQL</productname> extensions.
See below for details on compatibility issues.
ABSOLUTE fetches are not any faster than navigating to the desired row
with a relative move: the underlying implementation must traverse all
the intermediate rows anyway. Negative absolute fetches are even worse:
the query must be read to the end to find the last row, and then
traversed backward from there. However, rewinding to the start of the
query (as with FETCH ABSOLUTE 0) is fast.
</para>
<para>
@ -316,7 +395,7 @@ FETCH FORWARD 5 IN liahona;
</computeroutput>
-- Fetch previous row:
FETCH BACKWARD 1 IN liahona;
FETCH PRIOR FROM liahona;
<computeroutput>
code | title | did | date_prod | kind | len
@ -339,52 +418,39 @@ COMMIT WORK;
<refsect2 id="R2-SQL-FETCH-4">
<refsect2info>
<date>1998-09-01</date>
<date>2003-03-11</date>
</refsect2info>
<title>
SQL92
</title>
<para>
<note>
<para>
The non-embedded use of cursors is a <productname>PostgreSQL</productname>
extension. The syntax and usage of cursors is being compared
against the embedded form of cursors defined in <acronym>SQL92</acronym>.
</para>
</note>
</para>
<para>
<acronym>SQL92</acronym> allows absolute positioning of the cursor for
FETCH, and allows placing the results into explicit variables:
<acronym>SQL92</acronym> defines FETCH for use in embedded contexts only.
Therefore, it describes placing the results into explicit variables using
an <literal>INTO</> clause, for example:
<synopsis>
FETCH ABSOLUTE <replaceable class="PARAMETER">#</replaceable>
FETCH ABSOLUTE <replaceable class="PARAMETER">n</replaceable>
FROM <replaceable class="PARAMETER">cursor</replaceable>
INTO :<replaceable class="PARAMETER">variable</replaceable> [, ...]
</synopsis>
<variablelist>
<varlistentry>
<term>ABSOLUTE</term>
<listitem>
<para>
The cursor should be positioned to the specified absolute
row number. All row numbers in <productname>PostgreSQL</productname>
are relative numbers so this capability is not supported.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>:<replaceable class="PARAMETER">variable</replaceable></term>
<listitem>
<para>
Target host variable(s).
</para>
</listitem>
</varlistentry>
</variablelist>
<productname>PostgreSQL</productname>'s use of non-embedded cursors
is non-standard, and so is its practice of returning the result data
as if it were a SELECT result. Other than this point, FETCH is fully
upward-compatible with <acronym>SQL92</acronym>.
</para>
<para>
The FETCH forms involving FORWARD and BACKWARD (including the forms
FETCH <replaceable class="PARAMETER">count</replaceable> and FETCH ALL,
in which FORWARD is implicit) are <productname>PostgreSQL</productname>
extensions.
</para>
<para>
<acronym>SQL92</acronym> allows only <literal>FROM</> preceding the
cursor name; the option to use <literal>IN</> is an extension.
</para>
</refsect2>
</refsect1>

16
doc/src/sgml/ref/move.sgml
View file

@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/move.sgml,v 1.19 2003/03/10 03:53:49 tgl Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/move.sgml,v 1.20 2003/03/11 19:40:22 tgl Exp $
PostgreSQL documentation
-->
@ -21,7 +21,7 @@ PostgreSQL documentation
<date>1999-07-20</date>
</refsynopsisdivinfo>
<synopsis>
MOVE [ <replaceable class="PARAMETER">direction</replaceable> ] [ <replaceable class="PARAMETER">count</replaceable> ] { IN | FROM } <replaceable class="PARAMETER">cursor</replaceable>
MOVE [ <replaceable class="PARAMETER">direction</replaceable> { FROM | IN } ] <replaceable class="PARAMETER">cursor</replaceable>
</synopsis>
</refsynopsisdiv>
@ -33,9 +33,7 @@ MOVE [ <replaceable class="PARAMETER">direction</replaceable> ] [ <replaceable c
Description
</title>
<para>
<command>MOVE</command> allows the user to move the cursor position a
specified number of rows, or to the beginning or end of the cursor.
<command>MOVE ALL</command> moves to the end of the cursor.
<command>MOVE</command> repositions a cursor without retrieving any data.
<command>MOVE</command> works exactly like the <command>FETCH</command>
command, except it only repositions the cursor and does not return rows.
</para>
@ -54,8 +52,9 @@ MOVE [ <replaceable class="PARAMETER">direction</replaceable> ] [ <replaceable c
</title>
<para>
<command>MOVE</command> is a <productname>PostgreSQL</productname>
language extension.
The count returned in <command>MOVE</command>'s status string is the
count of the number of rows that would have been returned by the
equivalent <command>FETCH</command> command.
</para>
<para>
@ -119,9 +118,6 @@ COMMIT WORK;
</title>
<para>
There is no <acronym>SQL92</acronym> <command>MOVE</command> statement.
Instead, <acronym>SQL92</acronym> allows
one to <command>FETCH</command> rows from an absolute cursor position,
implicitly moving the cursor to the correct position.
</para>
</refsect2>
</refsect1>

300
src/backend/commands/portalcmds.c
View file

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/commands/portalcmds.c,v 1.9 2003/03/10 03:53:49 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/commands/portalcmds.c,v 1.10 2003/03/11 19:40:22 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -23,6 +23,11 @@
#include "rewrite/rewriteHandler.h"
static long DoRelativeFetch(Portal portal,
bool forward,
long count,
CommandDest dest);
static void DoPortalRewind(Portal portal);
static Portal PreparePortal(char *portalName);
@ -102,9 +107,7 @@ PerformCursorOpen(DeclareCursorStmt *stmt, CommandDest dest)
* PerformPortalFetch
* Execute SQL FETCH or MOVE command.
*
* name: name of portal
* forward: forward or backward fetch?
* count: # of tuples to fetch (INT_MAX means "all"; 0 means "refetch")
* stmt: parsetree node for command
* dest: where to send results
* completionTag: points to a buffer of size COMPLETION_TAG_BUFSIZE
* in which to store a command completion status string.
@ -112,9 +115,7 @@ PerformCursorOpen(DeclareCursorStmt *stmt, CommandDest dest)
* completionTag may be NULL if caller doesn't want a status string.
*/
void
PerformPortalFetch(char *name,
bool forward,
long count,
PerformPortalFetch(FetchStmt *stmt,
CommandDest dest,
char *completionTag)
{
@ -123,48 +124,150 @@ PerformPortalFetch(char *name,
/* initialize completion status in case of early exit */
if (completionTag)
strcpy(completionTag, (dest == None) ? "MOVE 0" : "FETCH 0");
/* sanity checks */
if (name == NULL)
{
elog(WARNING, "PerformPortalFetch: missing portal name");
return;
}
strcpy(completionTag, stmt->ismove ? "MOVE 0" : "FETCH 0");
/* get the portal from the portal name */
portal = GetPortalByName(name);
portal = GetPortalByName(stmt->portalname);
if (!PortalIsValid(portal))
{
elog(WARNING, "PerformPortalFetch: portal \"%s\" not found",
name);
stmt->portalname);
return;
}
/* Do it */
nprocessed = DoPortalFetch(portal, forward, count, dest);
nprocessed = DoPortalFetch(portal,
stmt->direction,
stmt->howMany,
stmt->ismove ? None : dest);
/* Return command status if wanted */
if (completionTag)
snprintf(completionTag, COMPLETION_TAG_BUFSIZE, "%s %ld",
(dest == None) ? "MOVE" : "FETCH",
stmt->ismove ? "MOVE" : "FETCH",
nprocessed);
}
/*
* DoPortalFetch
* Guts of PerformPortalFetch --- shared with SPI cursor operations
* Guts of PerformPortalFetch --- shared with SPI cursor operations.
* Caller must already have validated the Portal.
*
* Returns number of rows processed.
* Returns number of rows processed (suitable for use in result tag)
*/
long
DoPortalFetch(Portal portal, bool forward, long count, CommandDest dest)
DoPortalFetch(Portal portal,
FetchDirection fdirection,
long count,
CommandDest dest)
{
QueryDesc *queryDesc;
EState *estate;
MemoryContext oldcontext;
ScanDirection direction;
bool temp_desc = false;
bool forward;
switch (fdirection)
{
case FETCH_FORWARD:
if (count < 0)
{
fdirection = FETCH_BACKWARD;
count = -count;
}
/* fall out of switch to share code with FETCH_BACKWARD */
break;
case FETCH_BACKWARD:
if (count < 0)
{
fdirection = FETCH_FORWARD;
count = -count;
}
/* fall out of switch to share code with FETCH_FORWARD */
break;
case FETCH_ABSOLUTE:
if (count > 0)
{
/*
* Definition: Rewind to start, advance count-1 rows, return
* next row (if any). In practice, if the goal is less than
* halfway back to the start, it's better to scan from where
* we are. In any case, we arrange to fetch the target row
* going forwards.
*/
if (portal->posOverflow || portal->portalPos == LONG_MAX ||
count-1 <= portal->portalPos / 2)
{
DoPortalRewind(portal);
if (count > 1)
DoRelativeFetch(portal, true, count-1, None);
}
else
{
long pos = portal->portalPos;
if (portal->atEnd)
pos++; /* need one extra fetch if off end */
if (count <= pos)
DoRelativeFetch(portal, false, pos-count+1, None);
else if (count > pos+1)
DoRelativeFetch(portal, true, count-pos-1, None);
}
return DoRelativeFetch(portal, true, 1L, dest);
}
else if (count < 0)
{
/*
* Definition: Advance to end, back up abs(count)-1 rows,
* return prior row (if any). We could optimize this if we
* knew in advance where the end was, but typically we won't.
* (Is it worth considering case where count > half of size
* of query? We could rewind once we know the size ...)
*/
DoRelativeFetch(portal, true, FETCH_ALL, None);
if (count < -1)
DoRelativeFetch(portal, false, -count-1, None);
return DoRelativeFetch(portal, false, 1L, dest);
}
else /* count == 0 */
{
/* Rewind to start, return zero rows */
DoPortalRewind(portal);
return DoRelativeFetch(portal, true, 0L, dest);
}
break;
case FETCH_RELATIVE:
if (count > 0)
{
/*
* Definition: advance count-1 rows, return next row (if any).
*/
if (count > 1)
DoRelativeFetch(portal, true, count-1, None);
return DoRelativeFetch(portal, true, 1L, dest);
}
else if (count < 0)
{
/*
* Definition: back up abs(count)-1 rows, return prior row
* (if any).
*/
if (count < -1)
DoRelativeFetch(portal, false, -count-1, None);
return DoRelativeFetch(portal, false, 1L, dest);
}
else /* count == 0 */
{
/* Same as FETCH FORWARD 0, so fall out of switch */
fdirection = FETCH_FORWARD;
}
break;
default:
elog(ERROR, "DoPortalFetch: bogus direction");
break;
}
/*
* Get here with fdirection == FETCH_FORWARD or FETCH_BACKWARD,
* and count >= 0.
*/
forward = (fdirection == FETCH_FORWARD);
/*
* Zero count means to re-fetch the current row, if any (per SQL92)
@ -174,7 +277,7 @@ DoPortalFetch(Portal portal, bool forward, long count, CommandDest dest)
bool on_row;
/* Are we sitting on a row? */
on_row = (portal->atStart == false && portal->atEnd == false);
on_row = (!portal->atStart && !portal->atEnd);
if (dest == None)
{
@ -187,14 +290,12 @@ DoPortalFetch(Portal portal, bool forward, long count, CommandDest dest)
* If we are sitting on a row, back up one so we can re-fetch it.
* If we are not sitting on a row, we still have to start up and
* shut down the executor so that the destination is initialized
* and shut down correctly; so keep going. Further down in the
* routine, count == 0 means we will retrieve no row.
* and shut down correctly; so keep going. To DoRelativeFetch,
* count == 0 means we will retrieve no row.
*/
if (on_row)
{
DoPortalFetch(portal,
false /* backward */, 1L,
None /* throw away output */);
DoRelativeFetch(portal, false, 1L, None);
/* Set up to fetch one row forward */
count = 1;
forward = true;
@ -203,9 +304,44 @@ DoPortalFetch(Portal portal, bool forward, long count, CommandDest dest)
}
/*
* switch into the portal context
* Optimize MOVE BACKWARD ALL into a Rewind.
*/
oldcontext = MemoryContextSwitchTo(PortalGetHeapMemory(portal));
if (!forward && count == FETCH_ALL && dest == None)
{
long result = portal->portalPos;
if (result > 0 && !portal->atEnd)
result--;
DoPortalRewind(portal);
/* result is bogus if pos had overflowed, but it's best we can do */
return result;
}
return DoRelativeFetch(portal, forward, count, dest);
}
/*
* DoRelativeFetch
* Do fetch for a simple N-rows-forward-or-backward case.
*
* count <= 0 is interpreted as a no-op: the destination gets started up
* and shut down, but nothing else happens. Also, count == FETCH_ALL is
* interpreted as "all rows".
*
* Caller must already have validated the Portal.
*
* Returns number of rows processed (suitable for use in result tag)
*/
static long
DoRelativeFetch(Portal portal,
bool forward,
long count,
CommandDest dest)
{
QueryDesc *queryDesc;
EState *estate;
ScanDirection direction;
QueryDesc temp_queryDesc;
queryDesc = PortalGetQueryDesc(portal);
estate = queryDesc->estate;
@ -224,12 +360,9 @@ DoPortalFetch(Portal portal, bool forward, long count, CommandDest dest)
if (dest != queryDesc->dest &&
!(queryDesc->dest == RemoteInternal && dest == Remote))
{
QueryDesc *qdesc = (QueryDesc *) palloc(sizeof(QueryDesc));
memcpy(qdesc, queryDesc, sizeof(QueryDesc));
qdesc->dest = dest;
queryDesc = qdesc;
temp_desc = true;
memcpy(&temp_queryDesc, queryDesc, sizeof(QueryDesc));
temp_queryDesc.dest = dest;
queryDesc = &temp_queryDesc;
}
/*
@ -240,67 +373,103 @@ DoPortalFetch(Portal portal, bool forward, long count, CommandDest dest)
* robust about being called again if they've already returned NULL
* once.) Then call the executor (we must not skip this, because the
* destination needs to see a setup and shutdown even if no tuples are
* available). Finally, update the atStart/atEnd state depending on
* available). Finally, update the portal position state depending on
* the number of tuples that were retrieved.
*/
if (forward)
{
if (portal->atEnd || count == 0)
if (portal->atEnd || count <= 0)
direction = NoMovementScanDirection;
else
direction = ForwardScanDirection;
/* In the executor, zero count processes all portal rows */
if (count == INT_MAX)
/* In the executor, zero count processes all rows */
if (count == FETCH_ALL)
count = 0;
ExecutorRun(queryDesc, direction, count);
if (direction != NoMovementScanDirection)
{
long oldPos;
if (estate->es_processed > 0)
portal->atStart = false; /* OK to back up now */
if (count <= 0 || (long) estate->es_processed < count)
portal->atStart = false; /* OK to go backward now */
if (count == 0 ||
(unsigned long) estate->es_processed < (unsigned long) count)
portal->atEnd = true; /* we retrieved 'em all */
oldPos = portal->portalPos;
portal->portalPos += estate->es_processed;
/* portalPos doesn't advance when we fall off the end */
if (portal->portalPos < oldPos)
portal->posOverflow = true;
}
}
else
{
if (!portal->backwardOK)
elog(ERROR, "Cursor cannot scan backwards"
elog(ERROR, "Cursor can only scan forward"
"\n\tDeclare it with SCROLL option to enable backward scan");
if (portal->atStart || count == 0)
if (portal->atStart || count <= 0)
direction = NoMovementScanDirection;
else
direction = BackwardScanDirection;
/* In the executor, zero count processes all portal rows */
if (count == INT_MAX)
/* In the executor, zero count processes all rows */
if (count == FETCH_ALL)
count = 0;
ExecutorRun(queryDesc, direction, count);
if (direction != NoMovementScanDirection)
{
if (estate->es_processed > 0)
if (estate->es_processed > 0 && portal->atEnd)
{
portal->atEnd = false; /* OK to go forward now */
if (count <= 0 || (long) estate->es_processed < count)
portal->portalPos++; /* adjust for endpoint case */
}
if (count == 0 ||
(unsigned long) estate->es_processed < (unsigned long) count)
{
portal->atStart = true; /* we retrieved 'em all */
portal->portalPos = 0;
portal->posOverflow = false;
}
else
{
long oldPos;
oldPos = portal->portalPos;
portal->portalPos -= estate->es_processed;
if (portal->portalPos > oldPos ||
portal->portalPos <= 0)
portal->posOverflow = true;
}
}
}
/*
* Clean up and switch back to old context.
*/
if (temp_desc)
pfree(queryDesc);
MemoryContextSwitchTo(oldcontext);
return estate->es_processed;
}
/*
* DoPortalRewind - rewind a Portal to starting point
*/
static void
DoPortalRewind(Portal portal)
{
QueryDesc *queryDesc;
queryDesc = PortalGetQueryDesc(portal);
ExecutorRewind(queryDesc);
portal->atStart = true;
portal->atEnd = false;
portal->portalPos = 0;
portal->posOverflow = false;
}
/*
* PerformPortalClose
* Close a cursor.
@ -310,15 +479,6 @@ PerformPortalClose(char *name)
{
Portal portal;
/*
* sanity checks ... why is this case allowed by the grammar, anyway?
*/
if (name == NULL)
{
elog(WARNING, "PerformPortalClose: missing portal name");
return;
}
/*
* get the portal from the portal name
*/

38
src/backend/executor/execMain.c
View file

@ -26,7 +26,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/executor/execMain.c,v 1.201 2003/03/10 03:53:49 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/executor/execMain.c,v 1.202 2003/03/11 19:40:22 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -287,6 +287,42 @@ ExecutorEnd(QueryDesc *queryDesc)
queryDesc->planstate = NULL;
}
/* ----------------------------------------------------------------
* ExecutorRewind
*
* This routine may be called on an open queryDesc to rewind it
* to the start.
* ----------------------------------------------------------------
*/
void
ExecutorRewind(QueryDesc *queryDesc)
{
EState *estate;
MemoryContext oldcontext;
/* sanity checks */
Assert(queryDesc != NULL);
estate = queryDesc->estate;
Assert(estate != NULL);
/* It's probably not sensible to rescan updating queries */
Assert(queryDesc->operation == CMD_SELECT);
/*
* Switch into per-query memory context
*/
oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);
/*
* rescan plan
*/
ExecReScan(queryDesc->planstate, NULL);
MemoryContextSwitchTo(oldcontext);
}
/*
* ExecCheckRTPerms

9
src/backend/executor/spi.c
View file

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/executor/spi.c,v 1.87 2003/03/10 03:53:49 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/executor/spi.c,v 1.88 2003/03/11 19:40:22 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -1349,8 +1349,11 @@ _SPI_cursor_operation(Portal portal, bool forward, int count,
_SPI_current->tuptable = NULL;
/* Run the cursor */
_SPI_current->processed = DoPortalFetch(portal, forward, (long) count,
dest);
_SPI_current->processed =
DoPortalFetch(portal,
forward ? FETCH_FORWARD : FETCH_BACKWARD,
(long) count,
dest);
if (dest == SPI && _SPI_checktuples())
elog(FATAL, "SPI_fetch: # of processed tuples check failed");

245
src/backend/parser/gram.y
View file

@ -11,7 +11,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/parser/gram.y,v 2.405 2003/03/10 03:53:50 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/parser/gram.y,v 2.406 2003/03/11 19:40:23 tgl Exp $
*
* HISTORY
* AUTHOR DATE MAJOR EVENT
@ -191,7 +191,7 @@ static void doNegateFloat(Value *v);
%type <range> qualified_name OptConstrFromTable
%type <str> opt_id all_Op MathOp opt_name SpecialRuleRelation
%type <str> all_Op MathOp opt_name SpecialRuleRelation
%type <str> iso_level opt_encoding
%type <node> grantee
@ -248,12 +248,10 @@ static void doNegateFloat(Value *v);
%type <boolean> copy_from
%type <ival> direction reindex_type drop_type
%type <ival> reindex_type drop_type fetch_count
opt_column event comment_type cursor_options
%type <ival> fetch_how_many
%type <node> select_limit_value select_offset_value
%type <node> fetch_direction select_limit_value select_offset_value
%type <list> OptSeqList
%type <defelt> OptSeqElem
@ -345,7 +343,7 @@ static void doNegateFloat(Value *v);
EACH ELSE ENCODING ENCRYPTED END_P ESCAPE EXCEPT
EXCLUSIVE EXECUTE EXISTS EXPLAIN EXTERNAL EXTRACT
FALSE_P FETCH FLOAT_P FOR FORCE FOREIGN FORWARD
FALSE_P FETCH FIRST_P FLOAT_P FOR FORCE FOREIGN FORWARD
FREEZE FROM FULL FUNCTION
GLOBAL GRANT GROUP_P
@ -361,7 +359,7 @@ static void doNegateFloat(Value *v);
KEY
LANCOMPILER LANGUAGE LEADING LEFT LEVEL LIKE LIMIT
LANCOMPILER LANGUAGE LAST_P LEADING LEFT LEVEL LIKE LIMIT
LISTEN LOAD LOCAL LOCALTIME LOCALTIMESTAMP LOCATION
LOCK_P
@ -1239,16 +1237,15 @@ opt_drop_behavior:
;
/*****************************************************************************
*
* QUERY :
* close <optname>
* close <portalname>
*
*****************************************************************************/
ClosePortalStmt:
CLOSE opt_id
CLOSE name
{
ClosePortalStmt *n = makeNode(ClosePortalStmt);
n->portalname = $2;
@ -1256,10 +1253,6 @@ ClosePortalStmt:
}
;
opt_id: ColId { $$ = $1; }
| /*EMPTY*/ { $$ = NULL; }
;
/*****************************************************************************
*
@ -2583,61 +2576,17 @@ comment_text:
/*****************************************************************************
*
* QUERY:
* fetch/move [forward | backward] [ # | all ] [ in <portalname> ]
* fetch [ forward | backward | absolute | relative ]
* [ # | all | next | prior ] [ [ in | from ] <portalname> ]
* fetch/move
*
*****************************************************************************/
FetchStmt: FETCH direction fetch_how_many from_in name
FetchStmt: FETCH fetch_direction from_in name
{
FetchStmt *n = makeNode(FetchStmt);
if ($3 < 0)
{
$3 = -$3;
$2 = (($2 == FETCH_FORWARD) ? FETCH_BACKWARD : FETCH_FORWARD);
}
n->direction = $2;
n->howMany = $3;
n->portalname = $5;
n->ismove = FALSE;
$$ = (Node *)n;
}
| FETCH fetch_how_many from_in name
{
FetchStmt *n = makeNode(FetchStmt);
if ($2 < 0)
{
n->howMany = -$2;
n->direction = FETCH_BACKWARD;
}
else
{
n->direction = FETCH_FORWARD;
n->howMany = $2;
}
FetchStmt *n = (FetchStmt *) $2;
n->portalname = $4;
n->ismove = FALSE;
$$ = (Node *)n;
}
| FETCH direction from_in name
{
FetchStmt *n = makeNode(FetchStmt);
n->direction = $2;
n->howMany = 1;
n->portalname = $4;
n->ismove = FALSE;
$$ = (Node *)n;
}
| FETCH from_in name
{
FetchStmt *n = makeNode(FetchStmt);
n->direction = FETCH_FORWARD;
n->howMany = 1;
n->portalname = $3;
n->ismove = FALSE;
$$ = (Node *)n;
}
| FETCH name
{
FetchStmt *n = makeNode(FetchStmt);
@ -2647,55 +2596,13 @@ FetchStmt: FETCH direction fetch_how_many from_in name
n->ismove = FALSE;
$$ = (Node *)n;
}
| MOVE direction fetch_how_many from_in name
| MOVE fetch_direction from_in name
{
FetchStmt *n = makeNode(FetchStmt);
if ($3 < 0)
{
$3 = -$3;
$2 = (($2 == FETCH_FORWARD) ? FETCH_BACKWARD : FETCH_FORWARD);
}
n->direction = $2;
n->howMany = $3;
n->portalname = $5;
n->ismove = TRUE;
$$ = (Node *)n;
}
| MOVE fetch_how_many from_in name
{
FetchStmt *n = makeNode(FetchStmt);
if ($2 < 0)
{
n->howMany = -$2;
n->direction = FETCH_BACKWARD;
}
else
{
n->direction = FETCH_FORWARD;
n->howMany = $2;
}
FetchStmt *n = (FetchStmt *) $2;
n->portalname = $4;
n->ismove = TRUE;
$$ = (Node *)n;
}
| MOVE direction from_in name
{
FetchStmt *n = makeNode(FetchStmt);
n->direction = $2;
n->howMany = 1;
n->portalname = $4;
n->ismove = TRUE;
$$ = (Node *)n;
}
| MOVE from_in name
{
FetchStmt *n = makeNode(FetchStmt);
n->direction = FETCH_FORWARD;
n->howMany = 1;
n->portalname = $3;
n->ismove = TRUE;
$$ = (Node *)n;
}
| MOVE name
{
FetchStmt *n = makeNode(FetchStmt);
@ -2707,27 +2614,121 @@ FetchStmt: FETCH direction fetch_how_many from_in name
}
;
direction: FORWARD { $$ = FETCH_FORWARD; }
| BACKWARD { $$ = FETCH_BACKWARD; }
| RELATIVE { $$ = FETCH_FORWARD; }
| ABSOLUTE
fetch_direction:
/*EMPTY*/
{
elog(NOTICE,
"FETCH / ABSOLUTE not supported, using RELATIVE");
$$ = FETCH_FORWARD;
FetchStmt *n = makeNode(FetchStmt);
n->direction = FETCH_FORWARD;
n->howMany = 1;
$$ = (Node *)n;
}
| NEXT
{
FetchStmt *n = makeNode(FetchStmt);
n->direction = FETCH_FORWARD;
n->howMany = 1;
$$ = (Node *)n;
}
| PRIOR
{
FetchStmt *n = makeNode(FetchStmt);
n->direction = FETCH_BACKWARD;
n->howMany = 1;
$$ = (Node *)n;
}
| FIRST_P
{
FetchStmt *n = makeNode(FetchStmt);
n->direction = FETCH_ABSOLUTE;
n->howMany = 1;
$$ = (Node *)n;
}
| LAST_P
{
FetchStmt *n = makeNode(FetchStmt);
n->direction = FETCH_ABSOLUTE;
n->howMany = -1;
$$ = (Node *)n;
}
| ABSOLUTE fetch_count
{
FetchStmt *n = makeNode(FetchStmt);
n->direction = FETCH_ABSOLUTE;
n->howMany = $2;
$$ = (Node *)n;
}
| RELATIVE fetch_count
{
FetchStmt *n = makeNode(FetchStmt);
n->direction = FETCH_RELATIVE;
n->howMany = $2;
$$ = (Node *)n;
}
| fetch_count
{
FetchStmt *n = makeNode(FetchStmt);
n->direction = FETCH_FORWARD;
n->howMany = $1;
$$ = (Node *)n;
}
| ALL
{
FetchStmt *n = makeNode(FetchStmt);
n->direction = FETCH_FORWARD;
n->howMany = FETCH_ALL;
$$ = (Node *)n;
}
| FORWARD
{
FetchStmt *n = makeNode(FetchStmt);
n->direction = FETCH_FORWARD;
n->howMany = 1;
$$ = (Node *)n;
}
| FORWARD fetch_count
{
FetchStmt *n = makeNode(FetchStmt);
n->direction = FETCH_FORWARD;
n->howMany = $2;
$$ = (Node *)n;
}
| FORWARD ALL
{
FetchStmt *n = makeNode(FetchStmt);
n->direction = FETCH_FORWARD;
n->howMany = FETCH_ALL;
$$ = (Node *)n;
}
| BACKWARD
{
FetchStmt *n = makeNode(FetchStmt);
n->direction = FETCH_BACKWARD;
n->howMany = 1;
$$ = (Node *)n;
}
| BACKWARD fetch_count
{
FetchStmt *n = makeNode(FetchStmt);
n->direction = FETCH_BACKWARD;
n->howMany = $2;
$$ = (Node *)n;
}
| BACKWARD ALL
{
FetchStmt *n = makeNode(FetchStmt);
n->direction = FETCH_BACKWARD;
n->howMany = FETCH_ALL;
$$ = (Node *)n;
}
;
fetch_how_many:
fetch_count:
Iconst { $$ = $1; }
| '-' Iconst { $$ = - $2; }
| ALL { $$ = INT_MAX; }
| NEXT { $$ = 1; }
| PRIOR { $$ = -1; }
;
from_in: IN_P {}
| FROM {}
from_in: FROM {}
| IN_P {}
;
@ -7093,6 +7094,7 @@ unreserved_keyword:
| EXPLAIN
| EXTERNAL
| FETCH
| FIRST_P
| FORCE
| FORWARD
| FUNCTION
@ -7115,6 +7117,7 @@ unreserved_keyword:
| KEY
| LANCOMPILER
| LANGUAGE
| LAST_P
| LEVEL
| LISTEN
| LOAD
@ -7170,9 +7173,9 @@ unreserved_keyword:
| SCROLL
| SECOND_P
| SECURITY
| SESSION
| SEQUENCE
| SERIALIZABLE
| SESSION
| SET
| SHARE
| SHOW
@ -7211,8 +7214,8 @@ unreserved_keyword:
| VOLATILE
| WITH
| WITHOUT
| WRITE
| WORK
| WRITE
| YEAR_P
| ZONE
;

4
src/backend/parser/keywords.c
View file

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/parser/keywords.c,v 1.134 2003/02/10 04:44:46 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/parser/keywords.c,v 1.135 2003/03/11 19:40:23 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -128,6 +128,7 @@ static const ScanKeyword ScanKeywords[] = {
{"extract", EXTRACT},
{"false", FALSE_P},
{"fetch", FETCH},
{"first", FIRST_P},
{"float", FLOAT_P},
{"for", FOR},
{"force", FORCE},
@ -171,6 +172,7 @@ static const ScanKeyword ScanKeywords[] = {
{"key", KEY},
{"lancompiler", LANCOMPILER},
{"language", LANGUAGE},
{"last", LAST_P},
{"leading", LEADING},
{"left", LEFT},
{"level", LEVEL},

13
src/backend/tcop/utility.c
View file

@ -10,7 +10,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/tcop/utility.c,v 1.194 2003/03/10 03:53:51 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/tcop/utility.c,v 1.195 2003/03/11 19:40:23 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -321,15 +321,8 @@ ProcessUtility(Node *parsetree,
break;
case T_FetchStmt:
{
FetchStmt *stmt = (FetchStmt *) parsetree;
PerformPortalFetch(stmt->portalname,
stmt->direction == FETCH_FORWARD,
stmt->howMany,
(stmt->ismove) ? None : dest,
completionTag);
}
PerformPortalFetch((FetchStmt *) parsetree, dest,
completionTag);
break;
/*

18
src/backend/utils/mmgr/portalmem.c
View file

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/utils/mmgr/portalmem.c,v 1.52 2003/03/10 03:53:51 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/utils/mmgr/portalmem.c,v 1.53 2003/03/11 19:40:23 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -167,10 +167,12 @@ PortalSetQuery(Portal portal,
AssertArg(PortalIsValid(portal));
portal->queryDesc = queryDesc;
portal->backwardOK = ExecSupportsBackwardScan(queryDesc->plantree);
portal->atStart = true; /* Allow fetch forward only, to start */
portal->atEnd = false;
portal->cleanup = cleanup;
portal->backwardOK = ExecSupportsBackwardScan(queryDesc->plantree);
portal->atStart = true;
portal->atEnd = false; /* allow fetches */
portal->portalPos = 0;
portal->posOverflow = false;
}
/*
@ -211,10 +213,12 @@ CreatePortal(const char *name)
/* initialize portal query */
portal->queryDesc = NULL;
portal->backwardOK = false;
portal->atStart = true; /* disallow fetches until query is set */
portal->atEnd = true;
portal->cleanup = NULL;
portal->backwardOK = false;
portal->atStart = true;
portal->atEnd = true; /* disallow fetches until query is set */
portal->portalPos = 0;
portal->posOverflow = false;
/* put portal in table */
PortalHashTableInsert(portal);

10
src/include/commands/portalcmds.h
View file

@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $Id: portalcmds.h,v 1.5 2003/03/10 03:53:51 tgl Exp $
* $Id: portalcmds.h,v 1.6 2003/03/11 19:40:23 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -19,10 +19,12 @@
extern void PerformCursorOpen(DeclareCursorStmt *stmt, CommandDest dest);
extern void PerformPortalFetch(char *name, bool forward, long count,
CommandDest dest, char *completionTag);
extern void PerformPortalFetch(FetchStmt *stmt, CommandDest dest,
char *completionTag);
extern long DoPortalFetch(Portal portal, bool forward, long count,
extern long DoPortalFetch(Portal portal,
FetchDirection fdirection,
long count,
CommandDest dest);
extern void PerformPortalClose(char *name);

3
src/include/executor/executor.h
View file

@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $Id: executor.h,v 1.90 2003/03/10 03:53:51 tgl Exp $
* $Id: executor.h,v 1.91 2003/03/11 19:40:23 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -86,6 +86,7 @@ extern void ExecutorStart(QueryDesc *queryDesc);
extern TupleTableSlot *ExecutorRun(QueryDesc *queryDesc,
ScanDirection direction, long count);
extern void ExecutorEnd(QueryDesc *queryDesc);
extern void ExecutorRewind(QueryDesc *queryDesc);
extern void ExecCheckRTPerms(List *rangeTable, CmdType operation);
extern void ExecEndPlan(PlanState *planstate, EState *estate);
extern void ExecConstraints(const char *caller, ResultRelInfo *resultRelInfo,

13
src/include/nodes/parsenodes.h
View file

@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $Id: parsenodes.h,v 1.232 2003/03/10 03:53:51 tgl Exp $
* $Id: parsenodes.h,v 1.233 2003/03/11 19:40:23 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -1228,16 +1228,21 @@ typedef struct ClosePortalStmt
*/
typedef enum FetchDirection
{
/* for these, howMany is how many rows to fetch; FETCH_ALL means ALL */
FETCH_FORWARD,
FETCH_BACKWARD
/* ABSOLUTE someday? */
FETCH_BACKWARD,
/* for these, howMany indicates a position; only one row is fetched */
FETCH_ABSOLUTE,
FETCH_RELATIVE
} FetchDirection;
#define FETCH_ALL LONG_MAX
typedef struct FetchStmt
{
NodeTag type;
FetchDirection direction; /* see above */
long howMany; /* number of rows */
long howMany; /* number of rows, or position argument */
char *portalname; /* name of portal (cursor) */
bool ismove; /* TRUE if MOVE */
} FetchStmt;

19
src/include/utils/portal.h
View file

@ -9,7 +9,7 @@
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $Id: portal.h,v 1.38 2003/03/10 03:53:52 tgl Exp $
* $Id: portal.h,v 1.39 2003/03/11 19:40:24 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -27,10 +27,21 @@ typedef struct PortalData
char *name; /* Portal's name */
MemoryContext heap; /* subsidiary memory */
QueryDesc *queryDesc; /* Info about query associated with portal */
bool backwardOK; /* is fetch backwards allowed at all? */
bool atStart; /* T => fetch backwards is not allowed now */
bool atEnd; /* T => fetch forwards is not allowed now */
void (*cleanup) (Portal); /* Cleanup routine (optional) */
bool backwardOK; /* is fetch backwards allowed? */
/*
* atStart, atEnd and portalPos indicate the current cursor position.
* portalPos is zero before the first row, N after fetching N'th row of
* query. After we run off the end, portalPos = # of rows in query, and
* atEnd is true. If portalPos overflows, set posOverflow (this causes
* us to stop relying on its value for navigation). Note that atStart
* implies portalPos == 0, but not the reverse (portalPos could have
* overflowed).
*/
bool atStart;
bool atEnd;
bool posOverflow;
long portalPos;
} PortalData;
/*