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Provide a FORCE NULL option to COPY in CSV mode.

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This forces an input field containing the quoted null string to be
returned as a NULL. Without this option, only unquoted null strings
behave this way. This helps where some CSV producers insist on quoting
every field, whether or not it is needed. The option takes a list of
fields, and only applies to those columns. There is an equivalent
column-level option added to file_fdw.

Ian Barwick, with some tweaking by Andrew Dunstan, reviewed by Payal
Singh.
This commit is contained in:
Andrew Dunstan
2014-03-04 17:31:59 -05:00
parent e2a0fc5363
commit 3b5e03dca2
10 changed files with 308 additions and 35 deletions
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71
contrib/file_fdw/file_fdw.c
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@ -48,9 +48,9 @@ struct FileFdwOption
/*
* Valid options for file_fdw.
* These options are based on the options for COPY FROM command.
* But note that force_not_null is handled as a boolean option attached to
* each column, not as a table option.
* These options are based on the options for the COPY FROM command.
* But note that force_not_null and force_null are handled as boolean options
* attached to a column, not as table options.
*
* Note: If you are adding new option for user mapping, you need to modify
* fileGetOptions(), which currently doesn't bother to look at user mappings.
@ -69,7 +69,7 @@ static const struct FileFdwOption valid_options[] = {
{"null", ForeignTableRelationId},
{"encoding", ForeignTableRelationId},
{"force_not_null", AttributeRelationId},
{"force_null", AttributeRelationId},
/*
* force_quote is not supported by file_fdw because it's for COPY TO.
*/
@ -187,6 +187,7 @@ file_fdw_validator(PG_FUNCTION_ARGS)
Oid catalog = PG_GETARG_OID(1);
char *filename = NULL;
DefElem *force_not_null = NULL;
DefElem *force_null = NULL;
List *other_options = NIL;
ListCell *cell;
@ -243,10 +244,10 @@ file_fdw_validator(PG_FUNCTION_ARGS)
}
/*
* Separate out filename and force_not_null, since ProcessCopyOptions
* won't accept them. (force_not_null only comes in a boolean
* per-column flavor here.)
* Separate out filename and column-specific options, since
* ProcessCopyOptions won't accept them.
*/
if (strcmp(def->defname, "filename") == 0)
{
if (filename)
@ -255,16 +256,42 @@ file_fdw_validator(PG_FUNCTION_ARGS)
errmsg("conflicting or redundant options")));
filename = defGetString(def);
}
/*
* force_not_null is a boolean option; after validation we can discard
* it - it will be retrieved later in get_file_fdw_attribute_options()
*/
else if (strcmp(def->defname, "force_not_null") == 0)
{
if (force_not_null)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("conflicting or redundant options")));
errmsg("conflicting or redundant options"),
errhint("option \"force_not_null\" supplied more than once for a column")));
if(force_null)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("conflicting or redundant options"),
errhint("option \"force_not_null\" cannot be used together with \"force_null\"")));
force_not_null = def;
/* Don't care what the value is, as long as it's a legal boolean */
(void) defGetBoolean(def);
}
/* See comments for force_not_null above */
else if (strcmp(def->defname, "force_null") == 0)
{
if (force_null)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("conflicting or redundant options"),
errhint("option \"force_null\" supplied more than once for a column")));
if(force_not_null)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("conflicting or redundant options"),
errhint("option \"force_null\" cannot be used together with \"force_not_null\"")));
force_null = def;
(void) defGetBoolean(def);
}
else
other_options = lappend(other_options, def);
}
@ -369,8 +396,9 @@ fileGetOptions(Oid foreigntableid,
* Retrieve per-column generic options from pg_attribute and construct a list
* of DefElems representing them.
*
* At the moment we only have "force_not_null", which should be combined into
* a single DefElem listing all such columns, since that's what COPY expects.
* At the moment we only have "force_not_null", and "force_null",
* which should each be combined into a single DefElem listing all such
* columns, since that's what COPY expects.
*/
static List *
get_file_fdw_attribute_options(Oid relid)
@ -380,6 +408,9 @@ get_file_fdw_attribute_options(Oid relid)
AttrNumber natts;
AttrNumber attnum;
List *fnncolumns = NIL;
List *fncolumns = NIL;
List *options = NIL;
rel = heap_open(relid, AccessShareLock);
tupleDesc = RelationGetDescr(rel);
@ -410,17 +441,29 @@ get_file_fdw_attribute_options(Oid relid)
fnncolumns = lappend(fnncolumns, makeString(attname));
}
}
else if (strcmp(def->defname, "force_null") == 0)
{
if (defGetBoolean(def))
{
char *attname = pstrdup(NameStr(attr->attname));
fncolumns = lappend(fncolumns, makeString(attname));
}
}
/* maybe in future handle other options here */
}
}
heap_close(rel, AccessShareLock);
/* Return DefElem only when some column(s) have force_not_null */
/* Return DefElem only when some column(s) have force_not_null / force_null options set */
if (fnncolumns != NIL)
return list_make1(makeDefElem("force_not_null", (Node *) fnncolumns));
else
return NIL;
options = lappend(options, makeDefElem("force_not_null", (Node *) fnncolumns));
if (fncolumns != NIL)
options = lappend(options,makeDefElem("force_null", (Node *) fncolumns));
return options;
}
/*