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@ -136,7 +136,7 @@ |
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AS 'SELECT \'None\'::text AS name, |
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1000 AS salary, |
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25 AS age, |
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\'none\'::char16 AS dept;' |
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\'none\'::text AS dept;' |
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LANGUAGE 'sql'; |
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</ProgramListing> |
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@ -263,7 +263,7 @@ The reason why, in general, we must use the function |
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<Para> |
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On the other hand, fixed-length types of any size may |
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be passed by-reference. For example, here is a sample |
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implementation of the <ProductName>Postgres</ProductName> char16 type: |
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implementation of a <ProductName>Postgres</ProductName> type: |
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<ProgramListing> |
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/* 16-byte structure, passed by reference */ |
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@ -305,7 +305,6 @@ The reason why, in general, we must use the function |
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structure, we might use a code fragment like this: |
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<ProgramListing> |
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#include "postgres.h" |
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#include "utils/palloc.h" |
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... |
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char buffer[40]; /* our source data */ |
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... |
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@ -322,20 +321,23 @@ The reason why, in general, we must use the function |
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Suppose <FileName>funcs.c</FileName> look like: |
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<ProgramListing> |
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#include <string.h> |
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#include "postgres.h" /* for char16, etc. */ |
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#include "utils/palloc.h" /* for palloc */ |
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#include "postgres.h" |
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int |
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add_one(int arg) |
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{ |
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return(arg + 1); |
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} |
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char16 * |
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concat16(char16 *arg1, char16 *arg2) |
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text * |
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concat_text(text *arg1, text *arg2) |
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{ |
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char16 *new_c16 = (char16 *) palloc(sizeof(char16)); |
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memset((void *) new_c16, 0, sizeof(char16)); |
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(void) strncpy(new_c16, arg1, 16); |
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return (char16 *)(strncat(new_c16, arg2, 16)); |
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int32 new_text_size = VARSIZE(arg1) + VARSIZE(arg2) - VARHDRSZ; |
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text *new_text = (text *) palloc(new_text_size); |
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memset((void *) new_text, 0, new_text_size); |
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VARSIZE(new_text) = new_text_size; |
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strncpy(VARDATA(new_text), VARDATA(arg1), VARSIZE(arg1)-VARHDRSZ); |
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strncat(VARDATA(new_text), VARDATA(arg2), VARSIZE(arg2)-VARHDRSZ); |
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return (new_text); |
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} |
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text * |
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copytext(text *t) |
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@ -364,7 +366,7 @@ The reason why, in general, we must use the function |
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CREATE FUNCTION add_one(int4) RETURNS int4 |
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AS 'PGROOT/tutorial/obj/funcs.so' LANGUAGE 'c'; |
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CREATE FUNCTION concat16(char16, char16) RETURNS char16 |
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CREATE FUNCTION concat_text(text, text) RETURNS text |
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AS 'PGROOT/tutorial/obj/funcs.so' LANGUAGE 'c'; |
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CREATE FUNCTION copytext(text) RETURNS text |
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@ -401,7 +403,7 @@ The reason why, in general, we must use the function |
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In the query above, we can define c_overpaid as: |
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<ProgramListing> |
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#include "postgres.h" /* for char16, etc. */ |
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#include "postgres.h" |
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#include "libpq-fe.h" /* for TUPLE */ |
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bool |
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c_overpaid(TUPLE t,/* the current instance of EMP */ |
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@ -426,7 +428,7 @@ The reason why, in general, we must use the function |
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is null. <Acronym>GetAttributeByName</Acronym> will align data properly |
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so you can cast its return value to the desired type. |
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For example, if you have an attribute name which is of |
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the type char16, the <Acronym>GetAttributeByName</Acronym> call would look |
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the type name, the <Acronym>GetAttributeByName</Acronym> call would look |
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like: |
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<ProgramListing> |
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char *str; |
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@ -517,8 +519,9 @@ Most of the header (include) files for <ProductName>Postgres</ProductName> |
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</Para> |
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<ListItem> |
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<Para> Most of the internal <ProductName>Postgres</ProductName> types are declared |
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in postgres.h, so it's usually a good idea to |
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include that file as well. |
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in postgres.h, so it's a good idea to always |
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include that file as well. Including postgres.h |
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will also include elog.h and palloc.h for you. |
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</Para> |
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<ListItem> |
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<Para> Compiling and loading your object code so that |
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Bruce Momjian
28 years ago