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Add the ability for the core grammar to have more than one parse target.

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This patch essentially allows gram.y to implement a family of related
syntax trees, rather than necessarily always parsing a list of SQL
statements.  raw_parser() gains a new argument, enum RawParseMode,
to say what to do.  As proof of concept, add a mode that just parses
a TypeName without any other decoration, and use that to greatly
simplify typeStringToTypeName().

In addition, invent a new SPI entry point SPI_prepare_extended() to
allow SPI users (particularly plpgsql) to get at this new functionality.
In hopes of making this the last variant of SPI_prepare(), set up its
additional arguments as a struct rather than direct arguments, and
promise that future additions to the struct can default to zero.
SPI_prepare_cursor() and SPI_prepare_params() can perhaps go away at
some point.

Discussion: https://postgr.es/m/4165684.1607707277@sss.pgh.pa.us
This commit is contained in:
Tom Lane
2021-01-04 11:03:22 -05:00
parent b49154b3b7
commit 844fe9f159
14 changed files with 268 additions and 83 deletions
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126
doc/src/sgml/spi.sgml
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@ -1105,6 +1105,11 @@ SPIPlanPtr SPI_prepare_cursor(const char * <parameter>command</parameter>, int <
for the <structfield>options</structfield> field of <structname>DeclareCursorStmt</structname>.
<function>SPI_prepare</function> always takes the cursor options as zero.
</para>
<para>
This function is now deprecated in favor
of <function>SPI_prepare_extended</function>.
</para>
</refsect1>
<refsect1>
@ -1176,6 +1181,122 @@ SPIPlanPtr SPI_prepare_cursor(const char * <parameter>command</parameter>, int <
<!-- *********************************************** -->
<refentry id="spi-spi-prepare-extended">
<indexterm><primary>SPI_prepare_extended</primary></indexterm>
<refmeta>
<refentrytitle>SPI_prepare_extended</refentrytitle>
<manvolnum>3</manvolnum>
</refmeta>
<refnamediv>
<refname>SPI_prepare_extended</refname>
<refpurpose>prepare a statement, without executing it yet</refpurpose>
</refnamediv>
<refsynopsisdiv>
<synopsis>
SPIPlanPtr SPI_prepare_extended(const char * <parameter>command</parameter>,
const SPIPrepareOptions * <parameter>options</parameter>)
</synopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>
<function>SPI_prepare_extended</function> creates and returns a prepared
statement for the specified command, but doesn't execute the command.
This function is equivalent to <function>SPI_prepare</function>,
with the addition that the caller can specify options to control
the parsing of external parameter references, as well as other facets
of query parsing and planning.
</para>
</refsect1>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><literal>const char * <parameter>command</parameter></literal></term>
<listitem>
<para>
command string
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>const SPIPrepareOptions * <parameter>options</parameter></literal></term>
<listitem>
<para>
struct containing optional arguments
</para>
</listitem>
</varlistentry>
</variablelist>
<para>
Callers should always zero out the entire <parameter>options</parameter>
struct, then fill whichever fields they want to set. This ensures forward
compatibility of code, since any fields that are added to the struct in
future will be defined to behave backwards-compatibly if they are zero.
The currently available <parameter>options</parameter> fields are:
</para>
<variablelist>
<varlistentry>
<term><literal>ParserSetupHook <parameter>parserSetup</parameter></literal></term>
<listitem>
<para>
Parser hook setup function
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>void * <parameter>parserSetupArg</parameter></literal></term>
<listitem>
<para>
pass-through argument for <parameter>parserSetup</parameter>
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>RawParseMode <parameter>parseMode</parameter></literal></term>
<listitem>
<para>
mode for raw parsing; <literal>RAW_PARSE_DEFAULT</literal> (zero)
produces default behavior
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>int <parameter>cursorOptions</parameter></literal></term>
<listitem>
<para>
integer bit mask of cursor options; zero produces default behavior
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Return Value</title>
<para>
<function>SPI_prepare_extended</function> has the same return conventions as
<function>SPI_prepare</function>.
</para>
</refsect1>
</refentry>
<!-- *********************************************** -->
<refentry id="spi-spi-prepare-params">
<indexterm><primary>SPI_prepare_params</primary></indexterm>
@ -1208,6 +1329,11 @@ SPIPlanPtr SPI_prepare_params(const char * <parameter>command</parameter>,
with the addition that the caller can specify parser hook functions
to control the parsing of external parameter references.
</para>
<para>
This function is now deprecated in favor
of <function>SPI_prepare_extended</function>.
</para>
</refsect1>
<refsect1>