'\" t
.\"     Title: SPI_cursor_open
.\"    Author: The PostgreSQL Global Development Group
.\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
.\"      Date: 2019
.\"    Manual: PostgreSQL 9.6.12 Documentation
.\"    Source: PostgreSQL 9.6.12
.\"  Language: English
.\"
.TH "SPI_CURSOR_OPEN" "3" "2019" "PostgreSQL 9.6.12" "PostgreSQL 9.6.12 Documentation"
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.SH "NAME"
SPI_cursor_open \- set up a cursor using a statement created with \fBSPI_prepare\fR
.SH "SYNOPSIS"
.sp
.nf
Portal SPI_cursor_open(const char * \fIname\fR, SPIPlanPtr \fIplan\fR,
                       Datum * \fIvalues\fR, const char * \fInulls\fR,
                       bool \fIread_only\fR)
.fi
.SH "DESCRIPTION"
.PP
\fBSPI_cursor_open\fR
sets up a cursor (internally, a portal) that will execute a statement prepared by
\fBSPI_prepare\fR\&. The parameters have the same meanings as the corresponding parameters to
\fBSPI_execute_plan\fR\&.
.PP
Using a cursor instead of executing the statement directly has two benefits\&. First, the result rows can be retrieved a few at a time, avoiding memory overrun for queries that return many rows\&. Second, a portal can outlive the current procedure (it can, in fact, live to the end of the current transaction)\&. Returning the portal name to the procedure\*(Aqs caller provides a way of returning a row set as result\&.
.PP
The passed\-in parameter data will be copied into the cursor\*(Aqs portal, so it can be freed while the cursor still exists\&.
.SH "ARGUMENTS"
.PP
const char * \fIname\fR
.RS 4
name for portal, or
NULL
to let the system select a name
.RE
.PP
SPIPlanPtr \fIplan\fR
.RS 4
prepared statement (returned by
\fBSPI_prepare\fR)
.RE
.PP
Datum * \fIvalues\fR
.RS 4
An array of actual parameter values\&. Must have same length as the statement\*(Aqs number of arguments\&.
.RE
.PP
const char * \fInulls\fR
.RS 4
An array describing which parameters are null\&. Must have same length as the statement\*(Aqs number of arguments\&.
.sp
If
\fInulls\fR
is
NULL
then
\fBSPI_cursor_open\fR
assumes that no parameters are null\&. Otherwise, each entry of the
\fInulls\fR
array should be
\*(Aq\ \&\*(Aq
if the corresponding parameter value is non\-null, or
\*(Aqn\*(Aq
if the corresponding parameter value is null\&. (In the latter case, the actual value in the corresponding
\fIvalues\fR
entry doesn\*(Aqt matter\&.) Note that
\fInulls\fR
is not a text string, just an array: it does not need a
\*(Aq\e0\*(Aq
terminator\&.
.RE
.PP
bool \fIread_only\fR
.RS 4
true
for read\-only execution
.RE
.SH "RETURN VALUE"
.PP
Pointer to portal containing the cursor\&. Note there is no error return convention; any error will be reported via
\fBelog\fR\&.