Cleanup RelaxedAliasChecking configuration setting (#7982)

Author: dyemanov

builds/install/misc/firebird.conf

@@ -676,32 +676,6 @@
 #BugcheckAbort = 0
 
 
-# ----------------------------
-# Relaxing relation alias checking rules in SQL
-#
-# Since Firebird 2.0, strict alias checking rules were implemented in the SQL
-# parser to accord with the SQL standard requirements. This setting allows
-# these rules to be relaxed in order to allow legacy applications to run on
-# Firebird 2.0.
-# A setting of 1 (true) allows the parser to resolve a qualified column reference
-# using the relation name, where an alias has been specified for that relation.
-#
-# For example, it allows a query such as:
-#       SELECT TABLE.X FROM TABLE A
-#
-# It is not recommended to enable this setting. It should be regarded as an
-# interim workaround for porting untidy legacy code, until it is possible to
-# revise such code.
-#
-# CAUTION!
-# There is no guarantee that this setting will be available in future Firebird
-# versions.
-#
-# Type: boolean
-#
-#RelaxedAliasChecking = 0
-
-
 # ----------------------------
 # The engine currently provides statement-level read consistency in READ COMMITTED
 # mode by default. In this mode, rec_version/no_rec_version transaction flags have

src/common/classes/MetaString.h

@@ -70,6 +70,7 @@ class MetaString
 
 	MetaString& assign(const char* s, FB_SIZE_T l);
 	MetaString& assign(const char* s) { return assign(s, s ? fb_strlen(s) : 0); }
+	MetaString& clear() { return assign(nullptr, 0); }
 	MetaString& operator=(const char* s) { return assign(s); }
 	MetaString& operator=(const AbstractString& s) { return assign(s.c_str(), s.length()); }
 	MetaString& operator=(const MetaString& m) { return set(m); }

src/common/config/config.h

@@ -153,7 +153,6 @@ enum ConfigKey
 	KEY_REDIRECTION,
 	KEY_DATABASE_GROWTH_INCREMENT,
 	KEY_FILESYSTEM_CACHE_THRESHOLD,
-	KEY_RELAXED_ALIAS_CHECKING,
 	KEY_TRACE_CONFIG,
 	KEY_MAX_TRACELOG_SIZE,
 	KEY_FILESYSTEM_CACHE_SIZE,
@@ -258,7 +257,6 @@ constexpr ConfigEntry entries[MAX_CONFIG_KEY] =
 	{TYPE_BOOLEAN,	"Redirection",				true,	false},
 	{TYPE_INTEGER,	"DatabaseGrowthIncrement",	false,	128 * 1048576},	// bytes
 	{TYPE_INTEGER,	"FileSystemCacheThreshold",	false,	65536},		// page buffers
-	{TYPE_BOOLEAN,	"RelaxedAliasChecking",		true,	false},		// if true relax strict alias checking rules in DSQL a bit
 	{TYPE_STRING,	"AuditTraceConfigFile",		true,	""},		// location of audit trace configuration file
 	{TYPE_INTEGER,	"MaxUserTraceLogSize",		true,	10},		// maximum size of user session trace log
 	{TYPE_INTEGER,	"FileSystemCacheSize",		true,	0},			// percent
@@ -578,8 +576,6 @@ class Config : public RefCounted, public GlobalStorage
 
 	CONFIG_GET_GLOBAL_KEY(FB_UINT64, getFileSystemCacheSize, KEY_FILESYSTEM_CACHE_SIZE, getInt);
 
-	CONFIG_GET_GLOBAL_BOOL(getRelaxedAliasChecking, KEY_RELAXED_ALIAS_CHECKING);
-
 	CONFIG_GET_GLOBAL_STR(getAuditTraceConfigFile, KEY_TRACE_CONFIG);
 
 	CONFIG_GET_GLOBAL_KEY(FB_UINT64, getMaxUserTraceLogSize, KEY_MAX_TRACELOG_SIZE, getInt);