Re: [Fwd: [PATCHES] Libpq support for precision and scale]

Your patch has been added to the PostgreSQL unapplied patches list at:

http://candle.pha.pa.us/cgi-bin/pgpatches

I will try to apply it within the next 48 hours.

---------------------------------------------------------------------------

Fernando Nasser wrote:
> This is a patch that was posted some time ago to pgsql-patches and
> no one has commented on it.
>
> It adds something that JDBC has that is not present in libpq (see below).
> Is it OK for inclusion?
>
> Regards to all and thanks for your time,
> Fernando
>
>
> -------- Original Message --------
> From: Fernando Nasser <fnasser(at)redhat(dot)com>
> Subject: [PATCHES] Libpq support for precision and scale
> To: pgsql-patches(at)postgresql(dot)org
>
> Some programs like utilities, IDEs, etc., frequently need to know the
> precision and scale of the result fields (columns). Unfortunately
> libpq does not have such routines yet (JDBC does).
>
> Liam and I created a few ones that do the trick, as inspired by the
> JDBC code. The functions are:
>
> char *PQftypename(const PGresult *res, int field_num);
>
> Returns the type name (not the name of the column, as PQfname do).
>
>
> int PQfprecision(const PGresult *res, int field_num);
> int PQfscale(const PGresult *res, int field_num);
>
> Return Scale and Precision of the type respectively.
>
>
> Most programs won't need this information and may not be willing
> to pay the overhead for metadata retrieval. Thus, we added
> an alternative function to be used instead of PQexec if one
> wishes extra metadata to be retrieved along with the query
> results:
>
> PGresult *PQexecIncludeMetadata(PGconn *conn, const char *query);
>
> It provides the same functionality and it is used in exactly the
> same way as PQexec but it includes extra metadata about the result
> fields. After this cal, it is possible to obtain the precision,
> scale and type name for each result field.
>
>
> The PQftypename function returns the internal PostgreSQL type name.
> As some programs may prefer something more user friendly than the
> internal type names, we've thrown in a conversion routine as well:
>
> char *PQtypeint2ext(const char *intname);
>
> This routine converts from the internal type name to a more user
> friendly type name convention.
>
>
> More details are in the patch to the SGML documentation that is
> part of the patch (attached).
>
>
> --
> Liam Stewart <liams(at)redhat(dot)com>
> Fernando Nasser <fnasser(at)redhat(dot)com>

> Index: fe-connect.c
> ===================================================================
> RCS file: /projects/cvsroot/pgsql/src/interfaces/libpq/fe-connect.c,v
> retrieving revision 1.180
> diff -c -p -r1.180 fe-connect.c
> *** fe-connect.c 2001/11/05 17:46:37 1.180
> --- fe-connect.c 2001/11/07 19:00:35
> *************** makeEmptyPGconn(void)
> *** 1849,1854 ****
> --- 1849,1855 ----
> #ifdef USE_SSL
> conn->allow_ssl_try = TRUE;
> #endif
> + conn->typecache = NULL;
>
> /*
> * The output buffer size is set to 8K, which is the usual size of
> *************** freePGconn(PGconn *conn)
> *** 1891,1896 ****
> --- 1892,1898 ----
> if (!conn)
> return;
> pqClearAsyncResult(conn); /* deallocate result and curTuple */
> + pqTypeCacheClear(conn); /* free all type cache entries */
> #ifdef USE_SSL
> if (conn->ssl)
> SSL_free(conn->ssl);
> Index: fe-exec.c
> ===================================================================
> RCS file: /projects/cvsroot/pgsql/src/interfaces/libpq/fe-exec.c,v
> retrieving revision 1.113
> diff -c -p -r1.113 fe-exec.c
> *** fe-exec.c 2001/10/25 05:50:13 1.113
> --- fe-exec.c 2001/11/07 19:00:35
> *************** char *const pgresStatus[] = {
> *** 48,53 ****
> --- 48,54 ----
> static void pqCatenateResultError(PGresult *res, const char *msg);
> static void saveErrorResult(PGconn *conn);
> static PGresult *prepareAsyncResult(PGconn *conn);
> + static PGresult *pqExec(PGconn *conn, const char *query, int metadata);
> static int addTuple(PGresult *res, PGresAttValue * tup);
> static void parseInput(PGconn *conn);
> static void handleSendFailure(PGconn *conn);
> *************** static int getRowDescriptions(PGconn *co
> *** 55,60 ****
> --- 56,63 ----
> static int getAnotherTuple(PGconn *conn, int binary);
> static int getNotify(PGconn *conn);
> static int getNotice(PGconn *conn);
> + static char *pqTypeCacheGet(PGconn *conn, Oid typenum);
> + static void pqTypeCachePut(PGconn *conn, Oid typenum, char *typename);
>
> /* ---------------
> * Escaping arbitrary strings to get valid SQL strings/identifiers.
> *************** addTuple(PGresult *res, PGresAttValue *
> *** 609,614 ****
> --- 612,678 ----
> return TRUE;
> }
>
> + /* Cache of the correspondence between type Oids and
> + * type names. Without it too many queries can be made to
> + * retrieve this same information from the catalog over and over.
> + */
> +
> + static char *
> + pqTypeCacheGet(PGconn *conn, Oid typenum)
> + {
> + char *typename = NULL;
> + PGtypecache *tc = conn->typecache;
> +
> + /* Look for type Oid. */
> + while (tc != NULL)
> + {
> + if (tc->typenum == typenum)
> + {
> + typename = tc->typename;
> + break;
> + }
> + else
> + tc = tc->next;
> + }
> + return typename;
> + }
> +
> + static void
> + pqTypeCachePut(PGconn *conn, Oid typenum, char *typename)
> + {
> + PGtypecache *typetocache;
> +
> + typetocache = (PGtypecache *) malloc(sizeof(PGtypecache));
> + if (typetocache == NULL)
> + {
> + fprintf(stderr, "pqTypeCachePut: malloc failed.\n");
> + return;
> + }
> +
> + typetocache->typenum = typenum;
> + typetocache->typename = strdup(typename);
> + typetocache->next = conn->typecache;
> + conn->typecache = typetocache;
> + }
> +
> + void
> + pqTypeCacheClear(PGconn *conn)
> + {
> + PGtypecache *tc;
> + PGtypecache *ntc;
> +
> + /* Free all tcache entries (and typenames). */
> + tc = conn->typecache;
> + conn->typecache = NULL;
> + while (tc != NULL)
> + {
> + if (tc->typename)
> + free(tc->typename);
> + ntc = tc->next;
> + free(tc);
> + tc = ntc;
> + }
> + }
>
> /*
> * PQsendQuery
> *************** PQgetResult(PGconn *conn)
> *** 1277,1301 ****
> return res;
> }
>
>
> /*
> ! * PQexec
> * send a query to the backend and package up the result in a PGresult
> *
> * If the query was not even sent, return NULL; conn->errorMessage is set to
> * a relevant message.
> * If the query was sent, a new PGresult is returned (which could indicate
> * either success or failure).
> * The user is responsible for freeing the PGresult via PQclear()
> * when done with it.
> */
>
> ! PGresult *
> ! PQexec(PGconn *conn, const char *query)
> {
> PGresult *result;
> PGresult *lastResult;
> bool savedblocking;
>
> /*
> * we assume anyone calling PQexec wants blocking behaviour, we force
> --- 1341,1381 ----
> return res;
> }
>
> + PGresult *
> + PQexec(PGconn *conn, const char *query)
> + {
> + /* Don't get metadata. */
> + return pqExec (conn, query, 0 /* no metadata */);
> + }
>
> + PGresult *
> + PQexecIncludeMetadata(PGconn *conn, const char *query)
> + {
> + /* Get metadata as well. */
> + return pqExec (conn, query, 1 /* with metadata */);
> + }
> +
> /*
> ! * pqExec
> * send a query to the backend and package up the result in a PGresult
> *
> * If the query was not even sent, return NULL; conn->errorMessage is set to
> * a relevant message.
> * If the query was sent, a new PGresult is returned (which could indicate
> * either success or failure).
> + * If it is called with metadata == 1, the metadata about the column
> + * results will be obtained and saved in the PGresult.
> * The user is responsible for freeing the PGresult via PQclear()
> * when done with it.
> */
>
> ! static PGresult *
> ! pqExec(PGconn *conn, const char *query, int metadata)
> {
> PGresult *result;
> PGresult *lastResult;
> bool savedblocking;
> + int i;
>
> /*
> * we assume anyone calling PQexec wants blocking behaviour, we force
> *************** PQexec(PGconn *conn, const char *query)
> *** 1363,1368 ****
> --- 1443,1501 ----
>
> if (PQsetnonblocking(conn, savedblocking) == -1)
> return NULL;
> +
> + /*
> + * If metadata is requested and everything is well, loop through
> + * the result fields grabing the required information.
> + */
> +
> + if (metadata && (lastResult->numAttributes > 0))
> + for (i = 0; i < lastResult->numAttributes; i++)
> + {
> + Oid typenum;
> + PGresult *result;
> + char *tempname;
> + static char query[] = "select typname from pg_type where oid = %lu";
> + char *fullquery;
> +
> + if ((typenum = lastResult->attDescs[i].typid) == 0)
> + continue;
> +
> + /* Look up the cache for the type name. */
> + tempname = pqTypeCacheGet(conn, typenum);
> +
> + /* If it is a type that we still don't know the name,
> + query for the type name and store it in the cache. */
> + if (tempname == NULL)
> + {
> + fullquery = malloc (sizeof(query)
> + + 20 /* if Oids become 64 bits */);
> + if (fullquery == NULL)
> + {
> + fprintf(stderr, "pqExec: malloc failed.\n");
> + return NULL;
> + }
> + /* If the typename was not in the cache, query the catalog
> + and add it to the cache */
> + snprintf(fullquery, sizeof(query) + 20, query, typenum);
> + result = PQexec(conn, fullquery);
> + free(fullquery);
> + if (!result || PQresultStatus(result) != PGRES_TUPLES_OK)
> + {
> + PQclear(result);
> + continue;
> + }
> + if (PQntuples(result) != 1 || PQnfields(result) != 1) {
> + PQclear(result);
> + continue;
> + }
> + pqTypeCachePut(conn, typenum, PQgetvalue(result, 0, 0));
> + tempname = pqTypeCacheGet(conn, typenum);
> + }
> +
> + lastResult->attDescs[i].atttypname = strdup(tempname);
> + }
> +
> return lastResult;
>
> errout:
> *************** PQftype(const PGresult *res, int field_n
> *** 2104,2109 ****
> --- 2237,2253 ----
> return InvalidOid;
> }
>
> + char *
> + PQftypeName(const PGresult *res, int field_num)
> + {
> + if (!check_field_number(res, field_num))
> + return NULL;
> + if (res->attDescs)
> + return res->attDescs[field_num].atttypname;
> + else
> + return NULL;
> + }
> +
> int
> PQfsize(const PGresult *res, int field_num)
> {
> *************** PQfmod(const PGresult *res, int field_nu
> *** 2124,2129 ****
> --- 2268,2330 ----
> return res->attDescs[field_num].atttypmod;
> else
> return 0;
> + }
> +
> + int
> + PQfprecision(const PGresult *res, int field_num)
> + {
> + int mod;
> + char *type;
> +
> + if ((type = PQftypeName(res, field_num)) == NULL)
> + return 0;
> + mod = PQfmod(res, field_num);
> +
> + if (strcmp(type, "numeric") == 0)
> + return ((0xFFFF0000) & mod) >> 16;
> + else if (strcmp(type, "int2") == 0)
> + return 5;
> + else if (strcmp(type, "int4") == 0)
> + return 10;
> + else if (strcmp(type, "int8") == 0)
> + return 19; /* It would be 20 if it was unsigned. */
> + else if (strcmp(type, "float4") == 0)
> + return 6;
> + else if (strcmp(type, "float8") == 0)
> + return 15;
> + else if (strcmp(type, "varchar") == 0 ||
> + strcmp(type, "bpchar") == 0 ||
> + strcmp(type, "char") == 0)
> + return mod - 4;
> + else if (strcmp(type, "varbit") == 0 ||
> + strcmp(type, "bit") == 0)
> + return mod;
> +
> + return -1;
> + }
> +
> + int
> + PQfscale(const PGresult *res, int field_num)
> + {
> + int mod;
> + char *type;
> +
> + if ((type = PQftypeName(res, field_num)) == NULL)
> + return 0;
> + mod = PQfmod(res, field_num);
> +
> + if (strcmp(type, "numeric") == 0)
> + return ((0x0000FFFF) & mod) - 4;
> + else if (strcmp(type, "int2") == 0 ||
> + strcmp(type, "int4") == 0 ||
> + strcmp(type, "int8") == 0)
> + return 0;
> + else if (strcmp(type, "float4") == 0)
> + return -1;
> + else if (strcmp(type, "float8") == 0)
> + return -1;
> +
> + return -1;
> }
>
> char *
> Index: fe-misc.c
> ===================================================================
> RCS file: /projects/cvsroot/pgsql/src/interfaces/libpq/fe-misc.c,v
> retrieving revision 1.60
> diff -c -p -r1.60 fe-misc.c
> *** fe-misc.c 2001/11/05 17:46:37 1.60
> --- fe-misc.c 2001/11/07 19:00:35
> *************** WSSE_GOODEXIT:
> *** 896,898 ****
> --- 896,974 ----
> }
>
> #endif
> +
> + char *
> + PQinternal2common(const char *intname)
> + {
> + static char *typename;
> +
> + if (intname == NULL)
> + return NULL;
> +
> + if (strcmp(intname, "int8") == 0)
> + typename = "bigint";
> + else if (strcmp(intname, "bit") == 0)
> + typename = "bit";
> + else if (strcmp(intname, "varbit") == 0)
> + typename = "varbit"; /* bit varying */
> + else if (strcmp(intname, "bool") == 0)
> + typename = "boolean";
> + else if (strcmp(intname, "box") == 0)
> + typename = "box";
> + else if (strcmp(intname, "bpchar") == 0)
> + typename = "char"; /* character */
> + else if (strcmp(intname, "varchar") == 0)
> + typename = "varchar"; /* character varying */
> + else if (strcmp(intname, "cidr") == 0)
> + typename = "cidr";
> + else if (strcmp(intname, "circle") == 0)
> + typename = "circle";
> + else if (strcmp(intname, "date") == 0)
> + typename = "date";
> + else if (strcmp(intname, "float8") == 0)
> + typename = "double precision";
> + else if (strcmp(intname, "inet") == 0)
> + typename = "inet";
> + else if (strcmp(intname, "int4") == 0)
> + typename = "integer";
> + else if (strcmp(intname, "interval") == 0)
> + typename = "interval";
> + else if (strcmp(intname, "line") == 0)
> + typename = "line";
> + else if (strcmp(intname, "lseg") == 0)
> + typename = "lseg";
> + else if (strcmp(intname, "macaddr") == 0)
> + typename = "macaddr";
> + else if (strcmp(intname, "decimal") == 0)
> + typename = "numeric";
> + else if (strcmp(intname, "numeric") == 0)
> + typename = "numeric";
> + else if (strcmp(intname, "oid") == 0)
> + typename = "oid";
> + else if (strcmp(intname, "path") == 0)
> + typename = "path";
> + else if (strcmp(intname, "point") == 0)
> + typename = "point";
> + else if (strcmp(intname, "polygon") == 0)
> + typename = "polygon";
> + else if (strcmp(intname, "float4") == 0)
> + typename = "real";
> + else if (strcmp(intname, "int2") == 0)
> + typename = "smallint";
> + else if (strcmp(intname, "serial") == 0)
> + typename = "serial";
> + else if (strcmp(intname, "text") == 0)
> + typename = "text";
> + else if (strcmp(intname, "time") == 0)
> + typename = "time";
> + else if (strcmp(intname, "time with time zone") == 0)
> + typename = "time with time zone";
> + else if (strcmp(intname, "timestamp") == 0)
> + typename = "timestamp";
> + else if (strcmp(intname, "timestamp with time zone") == 0)
> + typename = "timestamp with time zone";
> + else
> + typename = NULL;
> +
> + return typename;
> + }
> Index: libpq-fe.h
> ===================================================================
> RCS file: /projects/cvsroot/pgsql/src/interfaces/libpq/libpq-fe.h,v
> retrieving revision 1.79
> diff -c -p -r1.79 libpq-fe.h
> *** libpq-fe.h 2001/11/05 17:46:37 1.79
> --- libpq-fe.h 2001/11/07 19:00:35
> *************** extern "C"
> *** 256,261 ****
> --- 256,262 ----
>
> /* Simple synchronous query */
> extern PGresult *PQexec(PGconn *conn, const char *query);
> + extern PGresult *PQexecIncludeMetadata(PGconn *conn, const char *query);
> extern PGnotify *PQnotifies(PGconn *conn);
> extern void PQfreeNotify(PGnotify *notify);
>
> *************** extern "C"
> *** 303,315 ****
> extern char *PQfname(const PGresult *res, int field_num);
> extern int PQfnumber(const PGresult *res, const char *field_name);
> extern Oid PQftype(const PGresult *res, int field_num);
> extern int PQfsize(const PGresult *res, int field_num);
> extern int PQfmod(const PGresult *res, int field_num);
> extern char *PQcmdStatus(PGresult *res);
> extern char *PQoidStatus(const PGresult *res); /* old and ugly */
> extern Oid PQoidValue(const PGresult *res); /* new and improved */
> ! extern char *PQcmdTuples(PGresult *res);
> ! extern char *PQgetvalue(const PGresult *res, int tup_num, int field_num);
> extern int PQgetlength(const PGresult *res, int tup_num, int field_num);
> extern int PQgetisnull(const PGresult *res, int tup_num, int field_num);
>
> --- 304,319 ----
> extern char *PQfname(const PGresult *res, int field_num);
> extern int PQfnumber(const PGresult *res, const char *field_name);
> extern Oid PQftype(const PGresult *res, int field_num);
> + extern char *PQftypeName(const PGresult *res, int field_num);
> extern int PQfsize(const PGresult *res, int field_num);
> extern int PQfmod(const PGresult *res, int field_num);
> + extern int PQfprecision(const PGresult *res, int field_num);
> + extern int PQfscale(const PGresult *res, int field_num);
> extern char *PQcmdStatus(PGresult *res);
> extern char *PQoidStatus(const PGresult *res); /* old and ugly */
> extern Oid PQoidValue(const PGresult *res); /* new and improved */
> ! extern char *PQcmdTuples(PGresult *res);
> ! extern char *PQgetvalue(const PGresult *res, int tup_num, int field_num);
> extern int PQgetlength(const PGresult *res, int tup_num, int field_num);
> extern int PQgetisnull(const PGresult *res, int tup_num, int field_num);
>
> *************** extern "C"
> *** 371,376 ****
> --- 375,383 ----
> /* Get encoding id from environment variable PGCLIENTENCODING */
> extern int PQenv2encoding(void);
>
> + /* Convert internal type name to common type name */
> + extern char *PQinternal2common(const char *intname);
> +
> #ifdef __cplusplus
> }
> #endif
> Index: libpq-int.h
> ===================================================================
> RCS file: /projects/cvsroot/pgsql/src/interfaces/libpq/libpq-int.h,v
> retrieving revision 1.44
> diff -c -p -r1.44 libpq-int.h
> *** libpq-int.h 2001/11/05 17:46:38 1.44
> --- libpq-int.h 2001/11/07 19:00:35
> *************** union pgresult_data
> *** 75,88 ****
> char space[1]; /* dummy for accessing block as bytes */
> };
>
> ! /* Data about a single attribute (column) of a query result */
>
> typedef struct pgresAttDesc
> {
> ! char *name; /* type name */
> Oid typid; /* type id */
> int typlen; /* type size */
> int atttypmod; /* type-specific modifier info */
> } PGresAttDesc;
>
> /* Data for a single attribute of a single tuple */
> --- 75,91 ----
> char space[1]; /* dummy for accessing block as bytes */
> };
>
> ! /* Data about a single attribute (column) of a query result.
> ! * The type name is only available if PQexecIncludeMetadata() was used.
> ! */
>
> typedef struct pgresAttDesc
> {
> ! char *name; /* column name */
> Oid typid; /* type id */
> int typlen; /* type size */
> int atttypmod; /* type-specific modifier info */
> + char *atttypname; /* type name */
> } PGresAttDesc;
>
> /* Data for a single attribute of a single tuple */
> *************** typedef struct pgLobjfuncs
> *** 191,196 ****
> --- 194,208 ----
> Oid fn_lo_write; /* OID of backend function LOwrite */
> } PGlobjfuncs;
>
> + /* Entry in the cache of the correspondence between type Oids and type names.
> + */
> + typedef struct pgTypeCache
> + {
> + Oid typenum; /* OID of type */
> + char *typename; /* name of type */
> + struct pgTypeCache *next; /* name of type */
> + } PGtypecache;
> +
> /* PGconn stores all the state data associated with a single connection
> * to a backend.
> */
> *************** struct pg_conn
> *** 240,245 ****
> --- 252,258 ----
> char cryptSalt[2]; /* password salt received from backend */
> PGlobjfuncs *lobjfuncs; /* private state for large-object access
> * fns */
> + PGtypecache *typecache; /* cached types for this connection. */
>
> /* Buffer for data received from backend and not yet processed */
> char *inBuffer; /* currently allocated buffer */
> *************** extern void pqSetResultError(PGresult *r
> *** 305,310 ****
> --- 318,324 ----
> extern void *pqResultAlloc(PGresult *res, size_t nBytes, bool isBinary);
> extern char *pqResultStrdup(PGresult *res, const char *str);
> extern void pqClearAsyncResult(PGconn *conn);
> + extern void pqTypeCacheClear(PGconn *conn);
>
> /* === in fe-misc.c === */
>
>

> Index: libpq.sgml
> ===================================================================
> RCS file: /projects/cvsroot/pgsql/doc/src/sgml/libpq.sgml,v
> retrieving revision 1.72
> diff -c -p -r1.72 libpq.sgml
> *** libpq.sgml 2001/09/13 15:55:23 1.72
> --- libpq.sgml 2001/11/07 19:06:52
> *************** PGresult *PQexec(PGconn *conn,
> *** 728,733 ****
> --- 728,748 ----
> <function>PQerrorMessage</function> to get more information about the error.
> </para>
> </listitem>
> +
> + <listitem>
> + <para>
> + <function>PQexecIncludeMetadata</function>
> + Submit a query to the server and wait for the result;
> + include extra metadata about the result fields.
> + This makes available information such as the type name,
> + precision and scale for each field in the result.
> + <synopsis>
> + PGresult *PQexecIncludeMetadata(PGconn *conn,
> + const char *query);
> + </synopsis>
> + Used the same way as PQexec().
> + </para>
> + </listitem>
> </itemizedlist>
>
> <para>
> *************** You can query the system table <literal>
> *** 964,969 ****
> --- 979,986 ----
> the name and properties of the various data types. The <acronym>OID</acronym>s
> of the built-in data types are defined in <filename>src/include/catalog/pg_type.h</filename>
> in the source tree.
> + The function <function>PQftypename</function> can be used to retrieve the
> + type name if the result was obtained via <function>PQexecIncludeMetadata</function>.
> </para>
> </listitem>
>
> *************** extracts data from a <acronym>BINARY</ac
> *** 1010,1015 ****
> --- 1027,1126 ----
> </para>
> </listitem>
> </itemizedlist>
> +
> + <para>
> + The following functions only produce meaningful results if
> + <function>PQexecIncludeMetadata</function> was used
> + (as opposed to <function>PQexec</function>).
> + </para>
> +
> + <itemizedlist>
> +
> + <listitem>
> + <para>
> + <function>PQftypename</function>
> + Returns the name of the column type as a string.
> + Field indices start at 0.
> + <synopsis>
> + char *PQftypename(const PGresult *res,
> + int field_index);
> + </synopsis>
> + Returns the name of the column type as a string.
> + Copy the string if needed -- do not modify, free()
> + or assume its persistence. The internal type name is
> + returned; use PQtypeint2ext() to convert to a more SQL-ish style.
> + NULL is returned if the field type name is not availble.
> + </para>
> + </listitem>
> +
> + <listitem>
> + <para>
> + <function>PQfprecision</function>
> + Returns the precision of the field
> + associated with the given field index.
> + Field indices start at 0.
> + <synopsis>
> + int PQfprecision(const PGresult *res,
> + int field_index);
> + </synopsis>
> + Returns the precision of the field
> + associated with the given field index.
> + For numeric types (INTEGER, FLOAT, etc.), PQfprecision returns the
> + number of decimal digits in the specified field. For character and bit
> + string types, such as VARCHAR and BIT, PQfprecision returns the
> + maximum number of characters/bits allowed in the specified field.
> + PQfprecision returns 0 if precision information is not available and
> + -1 if precision is not applicable to the field in question. The latter
> + will be the case if the type of the field is POINT, for example.
> + </para>
> + </listitem>
> +
> + <listitem>
> + <para>
> + <function>PQfscale</function>
> + Returns the scale of the field
> + associated with the given field index.
> + Field indices start at 0.
> + <synopsis>
> + int PQfscale(const PGresult *res,
> + int field_index);
> + </synopsis>
> + Returns the scale of the field
> + associated with the given field index.
> + PQfscale returns the scale of the field associated with the given
> + field index. Scale is the number of digits after the decimal point,
> + so this function is useful only with fields that are of a numeric
> + type (INTEGER, FLOAT, NUMERIC, etc.). -1 is returned if scale is not
> + applicable to the field type. 0 is returned if scale information is
> + not available.
> + </para>
> + </listitem>
> + </itemizedlist>
> +
> + <para>
> + Use the function below to convert internal type names (like the
> + ones returned by <function>PQftypename</function>) into something
> + more user-friendly.
> + </para>
> +
> + <itemizedlist>
> + <listitem>
> + <para>
> + <function>PQtypeint2ext</function>
> + Converts an internal type name into a SQL-ish
> + type name.
> + <synopsis>
> + char *PQtypeint2ext(const char **intname);
> + </synopsis>
> + Converts an internal type name into a SQL-ish
> + type name.
> + NULL is returned if the internal type is not recognized
> + (which will be the case if the type is a UDT).
> + </para>
> + </listitem>
> +
> + </itemizedlist>
> +
> </sect2>
>
> <sect2 id="libpq-exec-select-values">
>

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