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odbc_fdw.c
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/*----------------------------------------------------------
*
* foreign-data wrapper for ODBC
*
* Copyright (c) 2011, PostgreSQL Global Development Group
*
* This software is released under the PostgreSQL Licence.
*
* Author: Zheng Yang <[email protected]>
*
* IDENTIFICATION
* odbc_fdw/odbc_fdw.c
*
*----------------------------------------------------------
*/
#include "postgres.h"
#include <string.h>
#include "funcapi.h"
#include "access/reloptions.h"
#include "catalog/pg_foreign_server.h"
#include "catalog/pg_foreign_table.h"
#include "catalog/pg_user_mapping.h"
#include "catalog/pg_type.h"
#include "commands/defrem.h"
#include "commands/explain.h"
#include "foreign/fdwapi.h"
#include "foreign/foreign.h"
#include "utils/memutils.h"
#include "utils/builtins.h"
#include "utils/relcache.h"
#include "storage/lock.h"
#include "miscadmin.h"
#include <stdio.h>
#include <sql.h>
#include <sqlext.h>
PG_MODULE_MAGIC;
#define PROCID_TEXTEQ 67
#define PROCID_TEXTCONST 25
typedef struct odbcFdwExecutionState
{
AttInMetadata *attinmeta;
char *svr_dsn;
char *svr_database;
char *svr_schema;
char *svr_table;
char *svr_username;
char *svr_password;
SQLHSTMT stmt;
SQLHDBC dbc;
int num_of_result_cols;
int num_of_table_cols;
StringInfoData *table_columns;
bool first_iteration;
List *col_position_mask;
List *col_size_array;
char *sql_count;
} odbcFdwExecutionState;
struct odbcFdwOption
{
const char *optname;
Oid optcontext; /* Oid of catalog in which option may appear */
};
/*
* Array of valid options
*
*/
static struct odbcFdwOption valid_options[] =
{
/* Foreign server options */
{ "dsn", ForeignServerRelationId },
/* Foreign table options */
{ "database", ForeignTableRelationId },
{ "schema", ForeignTableRelationId },
{ "table", ForeignTableRelationId },
{ "sql_query", ForeignTableRelationId },
{ "sql_count", ForeignTableRelationId },
/* User mapping options */
{ "username", UserMappingRelationId },
{ "password", UserMappingRelationId },
/* Sentinel */
{ NULL, InvalidOid}
};
/*
* SQL functions
*/
extern Datum odbc_fdw_handler(PG_FUNCTION_ARGS);
extern Datum odbc_fdw_validator(PG_FUNCTION_ARGS);
PG_FUNCTION_INFO_V1(odbc_fdw_handler);
PG_FUNCTION_INFO_V1(odbc_fdw_validator);
/*
* FDW callback routines
*/
static FdwPlan *odbcPlanForeignScan(Oid foreigntableid, PlannerInfo *root, RelOptInfo *baserel);
static void odbcExplainForeignScan(ForeignScanState *node, ExplainState *es);
static void odbcBeginForeignScan(ForeignScanState *node, int eflags);
static TupleTableSlot *odbcIterateForeignScan(ForeignScanState *node);
static void odbcReScanForeignScan(ForeignScanState *node);
static void odbcEndForeignScan(ForeignScanState *node);
/*
* helper functions
*/
static bool odbcIsValidOption(const char *option, Oid context);
Datum
odbc_fdw_handler(PG_FUNCTION_ARGS)
{
FdwRoutine *fdwroutine = makeNode(FdwRoutine);
fdwroutine->PlanForeignScan = odbcPlanForeignScan;
fdwroutine->ExplainForeignScan = odbcExplainForeignScan;
fdwroutine->BeginForeignScan = odbcBeginForeignScan;
fdwroutine->IterateForeignScan = odbcIterateForeignScan;
fdwroutine->ReScanForeignScan = odbcReScanForeignScan;
fdwroutine->EndForeignScan = odbcEndForeignScan;
PG_RETURN_POINTER(fdwroutine);
}
/*
* Validate function
*/
Datum
odbc_fdw_validator(PG_FUNCTION_ARGS)
{
List *options_list = untransformRelOptions(PG_GETARG_DATUM(0));
Oid catalog = PG_GETARG_OID(1);
char *dsn = NULL;
char *svr_database = NULL;
char *svr_schema = NULL;
char *svr_table = NULL;
char *sql_query = NULL;
char *sql_count = NULL;
char *username = NULL;
char *password = NULL;
ListCell *cell;
#ifdef DEBUG
elog(DEBUG3, "odbc_fdw::odbc_fdw_validator");
#endif
/*
* Check that the necessary options: address, port, database
*/
foreach(cell, options_list)
{
DefElem *def = (DefElem *) lfirst(cell);
/* Complain invalid options */
if (!odbcIsValidOption(def->defname, catalog))
{
struct odbcFdwOption *opt;
StringInfoData buf;
/*
* Unknown option specified, complain about it. Provide a hint
* with list of valid options for the object.
*/
initStringInfo(&buf);
for (opt = valid_options; opt->optname; opt++)
{
if (catalog == opt->optcontext)
appendStringInfo(&buf, "%s%s", (buf.len > 0) ? ", " : "",
opt->optname);
}
ereport(ERROR,
(errcode(ERRCODE_FDW_INVALID_OPTION_NAME),
errmsg("invalid option \"%s\"", def->defname),
errhint("Valid options in this context are: %s", buf.len ? buf.data : "<none>")
));
}
/* Complain about redundent options */
if (strcmp(def->defname, "dsn") == 0)
{
if (dsn)
ereport(ERROR, (errcode(ERRCODE_SYNTAX_ERROR),
errmsg("conflicting or redundant options: dsn (%s)", defGetString(def))
));
dsn = defGetString(def);
}
else if (strcmp(def->defname, "database") == 0)
{
if (svr_database)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("conflicting or redundant options: database (%s)", defGetString(def))
));
svr_database = defGetString(def);
}
else if (strcmp(def->defname, "schema") == 0)
{
if (svr_schema)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("conflicting or redundant options: schema (%s)", defGetString(def))
));
svr_schema = defGetString(def);
}
else if (strcmp(def->defname, "table") == 0)
{
if (svr_table)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("conflicting or redundant options: table (%s)", defGetString(def))
));
svr_table = defGetString(def);
}
else if (strcmp(def->defname, "sql_query") == 0)
{
if (sql_query)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("conflicting or redundant options: sql_query (%s)", defGetString(def))
));
sql_query = defGetString(def);
}
else if (strcmp(def->defname, "sql_count") == 0)
{
if (sql_count)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("conflicting or redundant options: sql_count (%s)", defGetString(def))
));
sql_count = defGetString(def);
}
else if (strcmp(def->defname, "username") == 0)
{
if (username)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("conflicting or redundant options: username (%s)", defGetString(def))
));
username = defGetString(def);
}
else if (strcmp(def->defname, "password") == 0)
{
if (password)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("conflicting or redundant options: password (%s)", defGetString(def))
));
password = defGetString(def);
}
}
/* Complain about missing essential options: dsn */
if (!dsn && catalog == ForeignServerRelationId)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("missing essential information: dsn (Database Source Name)")
));
PG_RETURN_VOID();
}
/*
* Fetch the options for a odbc_fdw foreign table.
*/
static void
odbcGetOptions(Oid foreigntableid, char **svr_dsn, char **svr_database, char **svr_schema, char ** svr_table, char ** sql_query,
char **sql_count, char **username, char **password, List **mapping_list)
{
ForeignTable *table;
ForeignServer *server;
UserMapping *mapping;
List *options;
ListCell *lc;
#ifdef DEBUG
elog(DEBUG3, "odbc_fdw::odbcGetOptions");
#endif
/*
* Extract options from FDW objects.
*/
table = GetForeignTable(foreigntableid);
server = GetForeignServer(table->serverid);
mapping = GetUserMapping(GetUserId(), table->serverid);
options = NIL;
options = list_concat(options, table->options);
options = list_concat(options, server->options);
options = list_concat(options, mapping->options);
*mapping_list = NIL;
/* Loop through the options, and get the foreign table options */
foreach(lc, options)
{
DefElem *def = (DefElem *) lfirst(lc);
if (strcmp(def->defname, "dsn") == 0)
{
*svr_dsn = defGetString(def);
continue;
}
if (strcmp(def->defname, "database") == 0)
{
*svr_database = defGetString(def);
continue;
}
if (strcmp(def->defname, "schema") == 0)
{
*svr_schema = defGetString(def);
continue;
}
if (strcmp(def->defname, "table") == 0)
{
*svr_table = defGetString(def);
continue;
}
if (strcmp(def->defname, "sql_query") == 0)
{
*sql_query = defGetString(def);
continue;
}
if (strcmp(def->defname, "sql_count") == 0)
{
*sql_count = defGetString(def);
continue;
}
if (strcmp(def->defname, "username") == 0)
{
*username = defGetString(def);
continue;
}
if (strcmp(def->defname, "password") == 0)
{
*password = defGetString(def);
continue;
}
/* Column mapping goes here */
*mapping_list = lappend(*mapping_list, def);
}
#ifdef DEBUG
elog(DEBUG4, "odbc_fdw::odbcGetOptions: list length: %i", (*mapping_list)->length);
#endif
/* Default values, if required */
if (!*svr_dsn)
*svr_dsn = NULL;
if (!*svr_database)
*svr_database = NULL;
if (!*svr_schema)
*svr_schema = NULL;
if (!*svr_table)
*svr_table = NULL;
if (!*sql_query)
*sql_query = NULL;
if (!*sql_count)
*sql_count = NULL;
if (!*username)
*username = NULL;
if (!*password)
*password = NULL;
}
static void extract_error(char *fn,
SQLHANDLE handle,
SQLSMALLINT type)
{
SQLINTEGER i = 0;
SQLINTEGER native;
SQLCHAR state[ 7 ];
SQLCHAR text[256];
SQLSMALLINT len;
SQLRETURN ret;
elog(NOTICE,
"\n"
"The driver reported the following diagnostics whilst running "
"%s\n\n",
fn);
do
{
ret = SQLGetDiagRec(type, handle, ++i, state, &native, text,
sizeof(text), &len );
if (SQL_SUCCEEDED(ret))
elog(NOTICE, "%s:%ld:%ld:%s\n", state, (long int) i, (long int) native, text);
}
while( ret == SQL_SUCCESS );
}
/*
* Get name qualifier char
*/
static void
getNameQualifierChar(SQLHDBC dbc, StringInfoData *nq_char)
{
SQLCHAR name_qualifier_char[2];
#ifdef DUBUG
elog(DEBUG3, "odbc_fdw::getNameQualifierChar");
#endif
SQLGetInfo(dbc,
SQL_QUALIFIER_NAME_SEPARATOR,
(SQLPOINTER)&name_qualifier_char,
2,
NULL);
initStringInfo(nq_char);
appendStringInfo(nq_char, "%s", (char *) name_qualifier_char);
}
/*
* Get quote cahr
*/
static void
getQuoteChar(SQLHDBC dbc, StringInfoData *q_char)
{
SQLCHAR quote_char[2];
#ifdef DEBUG
elog(DEBUG3, "odbc_fdw::getQuoteChar");
#endif
SQLGetInfo(dbc,
SQL_IDENTIFIER_QUOTE_CHAR,
(SQLPOINTER)"e_char,
2,
NULL);
initStringInfo(q_char);
appendStringInfo(q_char, "%s", (char *) quote_char);
}
/*
* get table size of a table
*/
static void
odbcGetTableSize(char *svr_dsn, char *svr_database, char *svr_schema, char *svr_table,
char *username, char *password, char *sql_count, unsigned int *size)
{
SQLHENV env;
SQLHDBC dbc;
SQLHSTMT stmt;
SQLRETURN ret;
StringInfoData conn_str;
StringInfoData sql_str;
SQLCHAR OutConnStr[1024];
SQLSMALLINT OutConnStrLen;
SQLUBIGINT table_size;
SQLLEN indicator;
StringInfoData name_qualifier_char;
StringInfoData quote_char;
#ifdef DEBUG
elog(DEBUG3, "odbc_fdw::odbcGetTableSize");
#endif
/* Construct connection string */
initStringInfo(&conn_str);
if (svr_database != NULL)
appendStringInfo(&conn_str, "DSN=%s;DATABASE=%s;UID=%s;PWD=%s;", svr_dsn, svr_database, username, password);
else
appendStringInfo(&conn_str, "DSN=%s;UID=%s;PWD=%s;", svr_dsn, username, password);
#ifdef DEBUG
elog(DEBUG4, "odbc_fdw::odbcGetTableSize: Connection string: %s", conn_str.data);
#endif
/* Allocate an environment handle */
SQLAllocHandle(SQL_HANDLE_ENV, SQL_NULL_HANDLE, &env);
/* We want ODBC 3 support */
SQLSetEnvAttr(env, SQL_ATTR_ODBC_VERSION, (void *) SQL_OV_ODBC3, 0);
/* Allocate a connection handle */
SQLAllocHandle(SQL_HANDLE_DBC, env, &dbc);
/* Connect to the DSN */
ret = SQLDriverConnect(dbc, NULL, (SQLCHAR *) conn_str.data, SQL_NTS,
OutConnStr, 1024, &OutConnStrLen, SQL_DRIVER_COMPLETE);
if (!SQL_SUCCEEDED(ret))
{
extract_error("SQLDriverConnect", dbc, SQL_HANDLE_DBC);
elog(ERROR, "odbc_fdw::odbcGetTableSize: Could not connect to driver");
}
else
{
#ifdef DEBUG
elog(DEBUG4, "odbc_fdw::odbcGetTableSize: Successfully connected to driver");
#endif
}
/* Allocate a statement handle */
SQLAllocHandle(SQL_HANDLE_STMT, dbc, &stmt);
if (sql_count == NULL)
{
/* Get quote char */
getQuoteChar(dbc, "e_char);
/* Get name qualifier char */
getNameQualifierChar(dbc, &name_qualifier_char);
initStringInfo(&sql_str);
appendStringInfo(&sql_str, "SELECT COUNT(*) FROM %s%s%s%s%s%s%s",
quote_char.data, svr_schema, quote_char.data,
name_qualifier_char.data,
quote_char.data, svr_table, quote_char.data);
}
else
{
initStringInfo(&sql_str);
appendStringInfo(&sql_str, "%s", sql_count);
}
#ifdef DEBUG
elog(DEBUG4, "odbc_fdw::odbcGetTableSize: Query: %s", sql_str.data);
#endif
ret = SQLExecDirect(stmt, (SQLCHAR *) sql_str.data, SQL_NTS);
if (SQL_SUCCEEDED(ret))
{
SQLFetch(stmt);
/* retrieve column data as a big int */
ret = SQLGetData(stmt, 1, SQL_C_UBIGINT, &table_size, 0, &indicator);
if (SQL_SUCCEEDED(ret))
{
*size = (unsigned int) table_size;
}
}
else
{
extract_error("SQLExecDirect", dbc, SQL_HANDLE_STMT);
elog(ERROR, "odbc_fdw::odbcGetTableSize: Could not retrieve table size");
}
/* Free handles, and disconnect */
if (stmt)
{
SQLFreeHandle(SQL_HANDLE_STMT, stmt);
stmt = NULL;
}
if (dbc)
{
SQLDisconnect(dbc);
SQLFreeHandle(SQL_HANDLE_DBC, dbc);
dbc = NULL;
}
if (env)
{
SQLFreeHandle(SQL_HANDLE_ENV, env);
env = NULL;
}
#ifdef DEBUG
elog(DEBUG4, "odbc_fdw::odbcGetTableSize: Count: %u", *size);
#endif
}
/*
* get quals in the select if there is one
*/
static void
odbcGetQual(Node *node, TupleDesc tupdesc, List *col_mapping_list, char **key, char **value, bool *pushdown)
{
ListCell *col_mapping;
*key = NULL;
*value = NULL;
*pushdown = false;
#ifdef DEBUG
elog(DEBUG3, "odbc_fdw::odbcGetQual");
#endif
if (!node)
return;
if (IsA(node, OpExpr))
{
OpExpr *op = (OpExpr *) node;
Node *left, *right;
Index varattno;
if (list_length(op->args) != 2)
return;
left = list_nth(op->args, 0);
if (!IsA(left, Var))
return;
varattno = ((Var *) left)->varattno;
right = list_nth(op->args, 1);
if (IsA(right, Const))
{
StringInfoData buf;
initStringInfo(&buf);
/* And get the column and value... */
*key = NameStr(tupdesc->attrs[varattno - 1]->attname);
#ifdef DEBUG
elog(DEBUG4, "odbc_fdw::odbcGetQual: constant type: %u", ((Const *) right)->consttype);
#endif
if (((Const *) right)->consttype == PROCID_TEXTCONST)
*value = TextDatumGetCString(((Const *) right)->constvalue);
else
{
return;
}
/* convert qual keys to mapped couchdb attribute name */
foreach(col_mapping, col_mapping_list)
{
DefElem *def = (DefElem *) lfirst(col_mapping);
if (strcmp(def->defname, *key) == 0)
{
*key = defGetString(def);
break;
}
}
/*
* We can push down this qual if:
* - The operatory is TEXTEQ
* - The qual is on the _id column (in addition, _rev column can be also valid)
*/
if (op->opfuncid == PROCID_TEXTEQ)
*pushdown = true;
#ifdef DEBUG
elog(DEBUG4, "odbc_fdw::odbcGetQual: Got qual %s = %s", *key, *value);
#endif
return;
}
}
return;
}
/*
* Check if the provided option is one of the valid options.
* context is the Oid of the catalog holding the object the option is for.
*/
static bool
odbcIsValidOption(const char *option, Oid context)
{
struct odbcFdwOption *opt;
#ifdef DEBUG
elog(DEBUG3, "odbc_fdw::odbcIsValidOption");
#endif
/* Check if the options presents in the valid option list */
for (opt = valid_options; opt->optname; opt++)
{
if (context == opt->optcontext && strcmp(opt->optname, option) == 0)
return true;
}
/* Foreign table may have anything as a mapping option */
if (context == ForeignTableRelationId)
return true;
else
return false;
}
/*
* odbcPlanForeignScan
* Create a FdwPlan for a scan on the foreign table
*/
static FdwPlan *
odbcPlanForeignScan(Oid foreigntableid, PlannerInfo *root, RelOptInfo *baserel)
{
FdwPlan *fdwplan;
unsigned int table_size = 0;
char *svr_dsn = NULL;
char *svr_database = NULL;
char *svr_schema = NULL;
char *svr_table = NULL;
char *sql_query = NULL;
char *sql_count = NULL;
char *username = NULL;
char *password = NULL;
List *col_mapping_list;
#ifdef DEBUG
elog(DEBUG3, "odbc_fdw::odbcPlanForeignScan");
#endif
/* Fetch the foreign table options */
odbcGetOptions(foreigntableid, &svr_dsn, &svr_database, &svr_schema, &svr_table, &sql_query,
&sql_count, &username, &password, &col_mapping_list);
fdwplan = makeNode(FdwPlan);
fdwplan->startup_cost = 10;
fdwplan->total_cost = 100 + fdwplan->startup_cost;
fdwplan->fdw_private = NIL; /* not used */
#ifdef DEBUG
elog(DEBUG4, "odbc_fdw::odbcPlanForeignScan: startup cost: %f", fdwplan->total_cost);
#endif
odbcGetTableSize(svr_dsn, svr_database, svr_schema, svr_table, username, password, sql_count, &table_size);
fdwplan->total_cost = fdwplan->total_cost + table_size;
#ifdef DEBUG
elog(DEBUG4, "odbc_fdw::odbcPlanForeignScan: total cost: %f", fdwplan->total_cost);
#endif
return fdwplan;
}
/*
* odbcBeginForeignScan
*
*/
static void
odbcBeginForeignScan(ForeignScanState *node, int eflags)
{
SQLHENV env;
SQLHDBC dbc;
odbcFdwExecutionState *festate;
SQLSMALLINT result_columns;
SQLHSTMT stmt;
SQLRETURN ret;
SQLCHAR OutConnStr[1024];
SQLSMALLINT OutConnStrLen;
#ifdef DEBUG
char dsn[256];
char desc[256];
SQLSMALLINT dsn_ret;
SQLSMALLINT desc_ret;
SQLUSMALLINT direction;
#endif
char *svr_dsn = NULL;
char *svr_database = NULL;
char *svr_schema = NULL;
char *svr_table = NULL;
char *sql_query = NULL;
char *sql_count = NULL;
char *username = NULL;
char *password = NULL;
StringInfoData conn_str;
Relation rel;
int num_of_columns;
StringInfoData *columns;
int i;
ListCell *col_mapping;
List *col_mapping_list;
StringInfoData sql;
StringInfoData col_str;
SQLCHAR quote_char[2];
SQLCHAR name_qualifier_char[2];
char *qual_key = NULL;
char *qual_value = NULL;
bool pushdown = FALSE;
#ifdef DEBUG
elog(DEBUG3, "odbc_fdw::odbcBeginForeignScan");
#endif
/* Fetch the foreign table options */
odbcGetOptions(RelationGetRelid(node->ss.ss_currentRelation), &svr_dsn, &svr_database, &svr_schema, &svr_table, &sql_query,
&sql_count, &username, &password, &col_mapping_list);
#ifdef DEBUG
elog(DEBUG4, "odbc_fdw::odbcBeginForeignScan: dsn: %s", svr_dsn);
elog(DEBUG4, "odbc_fdw::odbcBeginForeignScan: db: %s", svr_database);
elog(DEBUG4, "odbc_fdw::odbcBeginForeignScan: schema: %s", svr_schema);
elog(DEBUG4, "odbc_fdw::odbcBeginForeignScan: table: %s", svr_table);
elog(DEBUG4, "odbc_fdw::odbcBeginForeignScan: sql_query: %s", sql_query);
elog(DEBUG4, "odbc_fdw::odbcBeginForeignScan: sql_count: %s", sql_count);
elog(DEBUG4, "odbc_fdw::odbcBeginForeignScan: username: %s", username);
elog(DEBUG4, "odbc_fdw::odbcBeginForeignScan: password: %s", password);
#endif
initStringInfo(&conn_str);
if (svr_database != NULL)
appendStringInfo(&conn_str, "DSN=%s;DATABASE=%s;UID=%s;PWD=%s;", svr_dsn, svr_database, username, password);
else
appendStringInfo(&conn_str, "DSN=%s;UID=%s;PWD=%s;", svr_dsn, username, password);
#ifdef DEBUG
elog(DEBUG4, "odbc_fdw::odbcBeginForeignScan: connection string: %s", conn_str.data);
#endif
/* Allocate an environment handle */
SQLAllocHandle(SQL_HANDLE_ENV, SQL_NULL_HANDLE, &env);
/* We want ODBC 3 support */
SQLSetEnvAttr(env, SQL_ATTR_ODBC_VERSION, (void *) SQL_OV_ODBC3, 0);
#ifdef DEBUG
/* Print DSNs available: for debugging purposes */
direction = SQL_FETCH_FIRST;
while(SQL_SUCCEEDED(ret = SQLDataSources(env, direction,
(SQLCHAR *) dsn, sizeof(dsn), &dsn_ret,
(SQLCHAR *) desc, sizeof(desc), &desc_ret)))
{
direction = SQL_FETCH_NEXT;
elog(DEBUG5, "odbc_fdw::odbcBeginForeignScan: %s - %s", dsn, desc);
if (ret == SQL_SUCCESS_WITH_INFO) elog(NOTICE, "data truncation");
}
#endif
/* Allocate a connection handle */
SQLAllocHandle(SQL_HANDLE_DBC, env, &dbc);
/* Connect to the DSN */
ret = SQLDriverConnect(dbc, NULL, (SQLCHAR *) conn_str.data, SQL_NTS,
OutConnStr, 1024, &OutConnStrLen, SQL_DRIVER_COMPLETE);
if (!SQL_SUCCEEDED(ret)) {
extract_error("SQLDriverConnect", dbc, SQL_HANDLE_DBC);
elog(ERROR, "odbc_fdw::odbcBeginForeignScan: Could not connect to the driver");
}
else
{
#ifdef DEBUG
elog(DEBUG4, "odbc_fdw::odbcBeginForeignScan: Successfully connected to driver");
#endif
}
/* Getting the Quote char */
SQLGetInfo(dbc,
SQL_IDENTIFIER_QUOTE_CHAR,
(SQLPOINTER)"e_char,
2,
NULL);
/* Getting the Qualifier name separator */
SQLGetInfo(dbc,
SQL_QUALIFIER_NAME_SEPARATOR,
(SQLPOINTER)&name_qualifier_char,
2,
NULL);
#ifdef DEBUG
elog(DEBUG4, "odbc_fdw::odbcBeginForeignScan: QUOTE CHAR: %s", quote_char);
elog(DEBUG4, "odbc_fdw::odbcBeginForeignScan: SQL_QUALIFIER_NAME_SEPARATOR: %s", name_qualifier_char);
#endif
/* Fetch the table column info */
rel = heap_open(RelationGetRelid(node->ss.ss_currentRelation), AccessShareLock);
num_of_columns = rel->rd_att->natts;
columns = (StringInfoData *) palloc(sizeof(StringInfoData) * num_of_columns);
initStringInfo(&col_str);
for (i = 0; i < num_of_columns; i++)
{
StringInfoData col;
StringInfoData mapping;
bool mapped;
/* retrieve the column name */
initStringInfo(&col);
appendStringInfo(&col, "%s", NameStr(rel->rd_att->attrs[i]->attname));
mapped = FALSE;
/* check if the column name is mapping to a different name in remote table */
foreach(col_mapping, col_mapping_list)
{
DefElem *def = (DefElem *) lfirst(col_mapping);
if (strcmp(def->defname, col.data) == 0)
{
initStringInfo(&mapping);
appendStringInfo(&mapping, "%s", defGetString(def));
mapped = TRUE;
break;
}
}
/* decide which name is going to be used */
if (mapped)
columns[i] = mapping;
else
columns[i] = col;
appendStringInfo(&col_str, i == 0 ? "%s%s%s" : ",%s%s%s", (char *) quote_char, columns[i].data, (char *) quote_char);
}
heap_close(rel, NoLock);
#ifdef DEBUG
/* print out the actual column names in remote table for debug only*/
for (i = 0; i < num_of_columns; i++)
{
elog(DEBUG4, "odbc_fdw::odbcBeginForeignScan: Column Mapping %i: %s", i, columns[i].data);
}
elog(DEBUG4, "odbc_fdw::odbcBeginForeignScan: Column String: %s", col_str.data);
/*
// SUBSTRING supported
if (fFuncs & SQL_FN_STR_CHAR_LENGTH)
elog(DEBUG4, "odbc_fdw::odbcBeginForeignScan: HAS COUNT!"); // do something
// SUBSTRING not supported
else
elog(DEBUG4, "odbc_fdw::odbcBeginForeignScan: DUN HAVE!"); // do something else
*/
#endif
/* See if we've got a qual we can push down */
if (node->ss.ps.plan->qual)
{
ListCell *lc;
foreach (lc, node->ss.ps.qual)
{
/* Only the first qual can be pushed down to remote DBMS */
ExprState *state = lfirst(lc);
odbcGetQual((Node *) state->expr, node->ss.ss_currentRelation->rd_att, col_mapping_list, &qual_key, &qual_value, &pushdown);
if (pushdown)
break;
}
}
/* Construct the SQL statement used for remote querying */
initStringInfo(&sql);
if (pushdown)
{
if (svr_schema != NULL)
appendStringInfo(&sql, "SELECT %s FROM `%s`.`%s` WHERE `%s` = '%s'",
col_str.data, svr_schema, svr_table, qual_key, qual_value);
else
appendStringInfo(&sql, "SELECT %s FROM `%s` WHERE `%s` = '%s'",
col_str.data, svr_table, qual_key, qual_value);
}
else
{
/* Use custom query if it's available */
if (sql_query)
{
appendStringInfo(&sql, "%s", sql_query);
}
else
{
appendStringInfo(&sql, "SELECT %s FROM %s%s%s%s%s%s%s", col_str.data,
(char *) quote_char, svr_schema, (char *) quote_char,
(char *) name_qualifier_char, (char *) quote_char, svr_table, (char *) quote_char);
}
}
#ifdef DEBUG
elog(DEBUG4, "odbc_fdw::odbcBeginForeignScan: SQL: %s", sql.data);
#endif
/* Allocate a statement handle */
SQLAllocHandle(SQL_HANDLE_STMT, dbc, &stmt);
/* Retrieve a list of rows */
SQLExecDirect(stmt, (SQLCHAR *) sql.data, SQL_NTS);
SQLNumResultCols(stmt, &result_columns);
#ifdef DEBUG
elog(DEBUG4, "odbc_fdw::odbcBeginForeignScan: num of columns (begin): %i", (int) result_columns);
#endif
festate = (odbcFdwExecutionState *) palloc(sizeof(odbcFdwExecutionState));
festate->attinmeta = TupleDescGetAttInMetadata(node->ss.ss_currentRelation->rd_att);