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+'\" t
+.\"     Title: SPI_prepare
+.\"    Author: The PostgreSQL Global Development Group
+.\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
+.\"      Date: 2021
+.\"    Manual: PostgreSQL 13.4 Documentation
+.\"    Source: PostgreSQL 13.4
+.\"  Language: English
+.\"
+.TH "SPI_PREPARE" "3" "2021" "PostgreSQL 13.4" "PostgreSQL 13.4 Documentation"
+.\" -----------------------------------------------------------------
+.\" * Define some portability stuff
+.\" -----------------------------------------------------------------
+.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+.\" http://bugs.debian.org/507673
+.\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html
+.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+.ie \n(.g .ds Aq \(aq
+.el       .ds Aq '
+.\" -----------------------------------------------------------------
+.\" * set default formatting
+.\" -----------------------------------------------------------------
+.\" disable hyphenation
+.nh
+.\" disable justification (adjust text to left margin only)
+.ad l
+.\" -----------------------------------------------------------------
+.\" * MAIN CONTENT STARTS HERE *
+.\" -----------------------------------------------------------------
+.SH "NAME"
+SPI_prepare \- prepare a statement, without executing it yet
+.SH "SYNOPSIS"
+.sp
+.nf
+SPIPlanPtr SPI_prepare(const char * \fIcommand\fR, int \fInargs\fR, Oid * \fIargtypes\fR)
+.fi
+.SH "DESCRIPTION"
+.PP
+\fBSPI_prepare\fR
+creates and returns a prepared statement for the specified command, but doesn\*(Aqt execute the command\&. The prepared statement can later be executed repeatedly using
+\fBSPI_execute_plan\fR\&.
+.PP
+When the same or a similar command is to be executed repeatedly, it is generally advantageous to perform parse analysis only once, and might furthermore be advantageous to re\-use an execution plan for the command\&.
+\fBSPI_prepare\fR
+converts a command string into a prepared statement that encapsulates the results of parse analysis\&. The prepared statement also provides a place for caching an execution plan if it is found that generating a custom plan for each execution is not helpful\&.
+.PP
+A prepared command can be generalized by writing parameters ($1,
+$2, etc\&.) in place of what would be constants in a normal command\&. The actual values of the parameters are then specified when
+\fBSPI_execute_plan\fR
+is called\&. This allows the prepared command to be used over a wider range of situations than would be possible without parameters\&.
+.PP
+The statement returned by
+\fBSPI_prepare\fR
+can be used only in the current invocation of the C function, since
+\fBSPI_finish\fR
+frees memory allocated for such a statement\&. But the statement can be saved for longer using the functions
+\fBSPI_keepplan\fR
+or
+\fBSPI_saveplan\fR\&.
+.SH "ARGUMENTS"
+.PP
+const char * \fIcommand\fR
+.RS 4
+command string
+.RE
+.PP
+int \fInargs\fR
+.RS 4
+number of input parameters ($1,
+$2, etc\&.)
+.RE
+.PP
+Oid * \fIargtypes\fR
+.RS 4
+pointer to an array containing the
+OIDs of the data types of the parameters
+.RE
+.SH "RETURN VALUE"
+.PP
+\fBSPI_prepare\fR
+returns a non\-null pointer to an
+SPIPlan, which is an opaque struct representing a prepared statement\&. On error,
+NULL
+will be returned, and
+\fISPI_result\fR
+will be set to one of the same error codes used by
+\fBSPI_execute\fR, except that it is set to
+SPI_ERROR_ARGUMENT
+if
+\fIcommand\fR
+is
+NULL, or if
+\fInargs\fR
+is less than 0, or if
+\fInargs\fR
+is greater than 0 and
+\fIargtypes\fR
+is
+NULL\&.
+.SH "NOTES"
+.PP
+If no parameters are defined, a generic plan will be created at the first use of
+\fBSPI_execute_plan\fR, and used for all subsequent executions as well\&. If there are parameters, the first few uses of
+\fBSPI_execute_plan\fR
+will generate custom plans that are specific to the supplied parameter values\&. After enough uses of the same prepared statement,
+\fBSPI_execute_plan\fR
+will build a generic plan, and if that is not too much more expensive than the custom plans, it will start using the generic plan instead of re\-planning each time\&. If this default behavior is unsuitable, you can alter it by passing the
+CURSOR_OPT_GENERIC_PLAN
+or
+CURSOR_OPT_CUSTOM_PLAN
+flag to
+\fBSPI_prepare_cursor\fR, to force use of generic or custom plans respectively\&.
+.PP
+Although the main point of a prepared statement is to avoid repeated parse analysis and planning of the statement,
+PostgreSQL
+will force re\-analysis and re\-planning of the statement before using it whenever database objects used in the statement have undergone definitional (DDL) changes since the previous use of the prepared statement\&. Also, if the value of
+search_path
+changes from one use to the next, the statement will be re\-parsed using the new
+\fIsearch_path\fR\&. (This latter behavior is new as of
+PostgreSQL
+9\&.3\&.) See
+\fBPREPARE\fR(7)
+for more information about the behavior of prepared statements\&.
+.PP
+This function should only be called from a connected C function\&.
+.PP
+SPIPlanPtr
+is declared as a pointer to an opaque struct type in
+spi\&.h\&. It is unwise to try to access its contents directly, as that makes your code much more likely to break in future revisions of
+PostgreSQL\&.
+.PP
+The name
+SPIPlanPtr
+is somewhat historical, since the data structure no longer necessarily contains an execution plan\&.